Three Point One S’mores Pi

Who doesn’t love s’mores? Campfire-toasted marshmallows, milk chocolate, and crispy graham crackers make a delightfully messy treat. This recipe draws on the classic campfire treat, but refines it with a rich chocolate custard, vanilla bean marshmallow créme, and browned butter graham cracker crust. We've decorated this version in honor of the number pi, but you can adorn your pie in any way you choose.

This pie uses a few techniques and ingredients that may be unfamiliar to you. We have chosen each method to maximize flavor and help you create a perfect, lump-free pie. For example, cooking the custard in a water bath guarantees that your eggs won’t curdle. Less than ten grams of flavorless thickeners replace almost a quarter pound of cornstarch, allowing the rich flavor of bittersweet chocolate to sing. These techniques come from modern food science innovation and are completely safe. They may seem difficult at first, but they can make some forms of cooking easier and more delicious when mastered. Besides, what better way to celebrate the number pi than by benefiting from some of the innovations that science has brought into the kitchen!

Full ingredient list:

930 grams/4 cups milk
200 grams/1 cup bittersweet chocolate (chips or finely grated)
6 grams/2 teaspoons Knox Brand Gelatin
420 grams/1.75 cups white sugar (divided)
3 grams/0.75 teaspoons xanthan gum
4.5 grams/0.75 teaspoons salt (divided)
6 large eggs
1 vanilla bean
190 grams/1.5 cups graham crackers crumbs
82 grams/6 tablespoons butter
90 grams/6 tablespoons water (divided)
100 grams/0.5 cups semisweet chocolate chips
1.5 grams/0.25 teaspoons cream of tartar
170/0.5 cups light corn syrup

Kitchen supplies needed:

Oven
Stove
Stand mixer
Countertop blender
Sous vide water bath (see step 2 for adaptations)
Medium saucepan
Bowls
Spoons and forks
Silicone spatula
Thin metal spatula
Rolling pin
Kitchen torch (see step 21 for adaptations)
Kitchen scale
Candy thermometer
2 gallon-size Ziploc freezer bags
1 sandwich size Ziploc bag
Plastic cling wrap
Computer and printer (optional)

Step 1: Rich Chocolate Custard Ingredients

930 grams/4 cups milk
200 grams/1 cup bittersweet chocolate (chips or finely grated)
6 grams/2 teaspoons Knox brand gelatin
240 grams/1 cup white sugar
3 grams/0.75 teaspoons xanthan Gum
3 grams/0.5 teaspoons salt
2 large eggs
4 egg yolks from large eggs (reserve 2 egg whites for the marshmallow créme)
½ vanilla bean (reserve the other half for the marshmallow créme)

Step 2: Preheat a Water Bath

Preheat a water bath to 83 degrees C/181 degrees F. If you do not have a dedicated sous vide water bath, you can create one by placing a large pot of water on a small burner. Slowly adjust the heat until the temperature remains relatively constant. Make sure that this temperature does not go above 85 degrees C/185 degrees F.

Step 3: Prepare the Custard Base

In a large, microwave-safe bowl, mix together the milk and chocolate. Sprinkle the gelatin across the top of the milk and wait 10 minutes to allow the gelatin time to hydrate. Cover and microwave on high power for 2 minutes. Stir the mixture. Continue to microwave for 1 minute intervals until the chocolate melts into soft lumps upon stirring. The mixture will be warm, but not hot, and the chocolate will not be fully incorporated into the milk.

Transfer the mixture to a large blender.

Step 4: Add Ingredients to the Blender

Stir together the sugar, xanthan gum, and salt. Add this mixture to the blender.

Add the eggs to the blender.

Step 5: Prepare the Vanilla Bean

Place half a vanilla bean onto a cutting board. Vanilla beans are thick tubes filled with oily seeds. Cut lengthwise through the top of the tube. Then, spread the bean flat with your fingers so that the inside faces upwards. Scrape the seeds out of the vanilla bean with the knife and add to the blender. Reserve the flattened pod for later.

Step 6: Blend the Custard Base

Cover the blender and hold the lid down tightly with your hand. Pulse the blender on a slow speed, and then slowly increase the speed until the mixture comes together completely. Continue blending for an additional thirty seconds.

Step 7: Transfer Custard Base to a Bag

Pour the contents of the blender into a gallon-sized Ziploc freezer bag (other brands and thinner bags may not be able to withstand the heat). Add the vanilla bean pod to the bag. Zip up all of the bag except for one corner so that air can escape the bag. Carefully drape the bag over the flat edge of a table and slowly allow the bag to move downwards, pushing almost all air out of the bag. Seal the bag and ensure that the seal is tight.

Step 8: Cook the Custard

Submerge the freezer bag in the water bath with the zipper pointed upwards. Cook in the bath for 30 minutes. Remove and agitate the contents of the bag. Return to the water bath for 30 more minutes.

Step 9: Crush the Graham Crackers

While the custard is cooking, place about 12 graham crackers in a large zip-top bag and then crush with a rolling pin.

Step 10: Graham Cracker Crust Ingredients

Measure out the following ingredients:

190 grams/1.5 cups graham crackers crumbs
82 grams/6 tablespoons butter

Preheat the oven to 180 degrees C/350 degrees F. Grease the bottom and sides of a ceramic or glass 9-inch pie pan.

Step 11: Brown the Butter

Melt the butter in a saucepan over medium heat, stirring constantly. The butter will begin to bubble, lightly brown, and release a nutty aroma. When the butter reaches your desired level of brownness, remove from the heat and immediately mix in the graham cracker crumbs. This will prevent the browned butter from cooking further.

Step 12: Assemble Crust

Add 30 grams/2 tablespoons of water to the graham cracker mixture and stir until fully incorporated. Pour the graham cracker mixture into the pie pan. Using your hands, press the pie crust firmly to cover the bottom and sides. Place on the middle rack in the oven for 10-15 minutes, until the color of the crust becomes light brown. Allow the crust to cool for at least 30 minutes.

Step 13: Fill the Crust

Remove the custard from the water bath. Thoroughly dry the outside of the bag. Discard the vanilla bean pod with a slotted spoon. Slowly pour the contents into the crust until it nearly reaches the top of the graham cracker crust. Depending on the depth of your pie pan, you may have some leftover pastry cream.

Cover the pie in plastic wrap and refrigerate overnight. The pie will set up into a thick custard. Despite using gelatin, the texture will be smooth, not at all chewy. (Note: Condensation will form and may disturb the surface of the custard. You can smooth this over by lightly stirring the top 5 millimeters (about .25 inches) of the custard with the backside of a fork after the pie has cooled for 3 hours. Dry or discard the wet plastic wrap, recover, and continue chilling for at least 4 more hours.)

Step 14: Prepare the Garnish

100 grams/.5 cups semisweet chocolate chips

Using a word processor, copy and paste the first 100 digits of pi into a new document. Highlight them and convert them to a bold, 36 point font (we used Adobe Gothic Sans Serif B). Place a space between each number. Insert the symbol pi and convert to a 340 point font (we used Adobe Ming Std L). Print this document and cover with wax paper.

Place the chocolate chips in a microwave safe cup. Microwave on high for 20 seconds. Remove from microwave and stir. Repeat until the chocolate is melted. Longer periods of time in the microwave will result in burning. Spoon the melted chocolate into a sandwich sized Ziploc bag. Cut off a tiny portion of the bag's corner. Trace the outline of each number and the large numeral pi by squeezing chocolate out of the hole you created. Refrigerate until ready to use, at least two hours.

Note: We chose not to temper the chocolate because we wanted the garnish to melt in the mouth immediately and not to crunch. Feel free to temper the chocolate if you prefer a firmer texture, although you may need to use a finer grade of chocolate.

Step 15: Marshmallow Créme Ingredients

Gather the ingredients for the vanilla bean marshmallow créme.

2 large egg whites (reserved from step 1)
1.5 grams/0.25 teaspoons cream of tartar
180 grams/0.75 cups white sugar
170 grams/0.5 cups light corn syrup
60 grams/0.25 cups water
1.5 grams/0.25 teaspoons salt
1/2 vanilla bean (reserved from step 1)

Step 16: Beat the Egg Whites

Allow the egg whites to come to room temperature. Place them and the cream of tartar in the bowl of the stand mixer. Beat on high until soft peaks form, about 2 minutes.

Step 17: Prepare the Vanilla Bean

Place the other half of the vanilla bean onto a cutting board. Cut lengthwise through the top of the bean. Then, spread the bean flat with your fingers so that the inside faces upwards. Scrape the seeds out of the vanilla bean with the knife.

Step 18: Prepare the Sugar Syrup

Add the sugar, corn syrup, water, salt, vanilla bean seeds, and vanilla bean pod to a medium saucepan. Place the candy thermometer in the saucepan. Stir constantly over medium heat until the thermometer reads 116 degrees C/240 degrees F. Remove the saucepan from heat and discard the vanilla bean pod.

Step 19: Mix the Marshmallow Créme

With the mixer on low, slowly spoon the hot sugar syrup into the egg white foam, one tablespoon at a time. Continue mixing on high until firm marshmallow créme forms, about 4-6 minutes. While mixing, you may need to scrape the mixture down into the bowl with a rubber spatula.

Step 20: Top the Pie With Marshmallow Créme

Remove the pie from the refrigerator. Take a scoop of marshmallow créme and place it on the pie. Spread it 1 centimeter (about 0.5 inches) thick using 2 spoons to stretch the créme. Continue adding marshmallow créme until the surface of the pie is covered. Move the back of the spoon in small circles across the pie to create swirled patterns.

Step 21: Toast the Marshmallow Créme

Light a kitchen torch. Hold the flame at a 45 degree angle and quickly sweep back and forth across the surface of the pie. The pie should be lightly toasted, but not burnt. Refrigerate for at least 30 minutes before adding the garnish.

If you do not have a kitchen torch, place the pie under a hot broiler until toasted, approximately 1 minute. As the heat may have reached the custard, refrigerate the pie for at least 4 hours before adding the garnish.

Step 22: Collect the Chocolate Garnish

Remove the Chocolate Pi Garnish from the refrigerator. Slowly scrape the pi symbol and numbers from the waxed paper with the thin metal spatula. Try not to handle the numbers with your hands, as your body heat may cause them to melt and deform.

Step 23: Garnish the Pie

Using the thin metal spatula, place the pi symbol in the center of the pie. Carefully add the numbers to the rest of the pie, placing them in random orientations. If numbers break, try to place the pieces next to each other. Discard any numbers that break beyond repair. Refrigerate the pie until ready to serve.

Note: We chose to arrange the numbers in a haphazard fashion. You can arrange them in any order you like.

Step 24: Serve and Enjoy

To serve the pie, grease a sharp knife with cooking spray. Cut out the pieces, wiping and regreasing the blade after each cut. Serve immediately after cutting.

Acknowledgements: The chocolate custard was adapted from a recipe by Lauren Weisenthal posted on Serious Eats and techniques from Modernist Cuisine at Home. The marshmallow créme was adapted from a recipe by Shauna Sever posted on Chow. 

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