I Pi = Log(-1): EYE PIE (Chocolate Cherry Almond Panna Cotta Pie) = LOG NEGATIVE ONE (Chocolate Almond Log)




Introduction: I Pi = Log(-1): EYE PIE (Chocolate Cherry Almond Panna Cotta Pie) = LOG NEGATIVE ONE (Chocolate Almond Log)

I love to bake, and my husband, Aaron, is a physicist, so we had a lot of fun creating this pi pie. Aaron thought a play on i as “eye” would be a good starting point, so he thought of the equation exp(i pi) = -1 . Taking the logarithm of both sides, this turns into i pi = log(-1) .

My first idea for an edible representation was to use panna cotta for the eyeball, since the jiggly-ness would be perfect (and sort of creepy). Cherry pie filling seemed a good choice to hold the panna cotta upright in a chocolate cookie pie crust. Cherry partners great with chocolate and almond, so this became the overall flavor scheme, including using marzipan for the iris. As a bonus, piping the “goo” from the cherry pie filling worked beautifully to make the eyeball’s veins.

For the log negative one, I thought of the traditional holiday yule log dessert. I imagined a strategically placed slice cut from the end of a yule log would easily turn it into the number one. Another small roll of the log could make the negative sign. To keep with the chocolate-almond flavor theme, I added almond meal to a flourless chocolate batter, made a fluffy almond-flavored filling, and used marzipan for leaves. The ganache used to frost the log does double duty as a pie layer, keeping the chocolate cookie crust from becoming soggy from the cherry pie filling.

Placed side by side (with a couple strips of paper to make an equals sign in the middle), this reads as “eye pie equals negative one log” or  “i pi = log(-1) ”!



2 T unflavored gelatin
2 c milk or half and half
3 c heavy cream
¾ c sugar
½ t salt
1 t vanilla extract
1 t almond extract or 1 T amaretto

Prepare the panna cotta mold
Mark, with tape, the outside of a large glass bowl at the location where the diameter is the same as the diameter of the pie plate you will be using. (I used a 2.5 qt Pyrex bowl.) This is the level to which you will pour the panna cotta mixture.

Make panna cotta
1. In small bowl, combine gelatin with ¾ cup of milk and set aside.
2. In a heavy-bottomed saucepan over medium heat, combine remaining milk, cream, sugar, and salt. Bring to a full boil, stirring to prevent burning and boiling over. Stir gelatin mixture into hot cream mixture until dissolved. Stir in vanilla and almond extracts.
3. Pour mixture into your prepared mold to the level marked. (see photo)Pour any extra into small bowl and refrigerate to enjoy later.
4. Carefully press and smooth a sheet of plastic wrap onto top of mixture to prevent a skin from forming. Refrigerate 8 hours or overnight before using.



22-25 chocolate sandwich cookies
3 T butter, melted

1. Place cookies in food processor and pulse until fine crumbs.
2. Pulse in melted butter until just combined.
3. Press firmly into a 9-inch pie plate using back of a spoon or small measuring cup.
4. Refrigerate at least 2 hours.

Step 3: For Both Pie & Log: DARK CHOCOLATE GANACHE

for the first layer in the pie AND for frosting the log

1 ½ c heavy cream
8 oz dark chocolate, chopped fine (If using dark chips, this is about 1 1/3 cups.)

1. Place chocolate in glass mixing bowl.
2. Heat cream to boiling point (microwaving is fine), then pour hot cream over chocolate.
3. Cover for 5 minutes, then gently stir until smooth. Do this as gently as possible to prevent air bubbles. (photo 1)
4. Pour about ¼ cup of melted ganache into chocolate pie crust. Refrigerate to set ganache.
5. Cover remaining ganache and allow to cool at room temperature until thick enough to use as frosting. (photo 2) This will take several hours. You can speed up the process by placing ganache in refrigerator and stirring at intervals.

Step 4: For Pie: CHERRY LAYER


20 oz can cherry pie filling (photo 1)
1 t vanilla extract
1 t almond extract or 1 T amaretto

1. Stir to combine.
2. Reserve a spoonful or two of the “goo” and place in small resealable bag. (photo 2)
3. Spread remaining filling on top of ganache in chocolate pie crust.



5 large eggs at room temperature, whites and yolks separated
5 T sugar
3 oz dark chocolate, melted and cooled (if using dark chips, this is about ½ cup)
¼ c almond meal
cocoa powder (for dusting)

1. Grease 11”x16”x3/4” jelly roll pan. Line pan with parchment paper (leave paper extending over sides; snip corners to fit). Grease and lightly flour paper.
2. Preheat oven to 350 degrees F.
3. In large metal mixing bowl, whip the egg whites until foamy. Gradually whip in 3 T of the sugar until stiff peaks form (5-6 minutes using a large stand mixer). Move egg whites to different bowl and set aside.
4. In same mixing bowl used to whip whites, whip egg yolks with remaining 2 T of sugar until very light-colored and fluffy (5-6 minutes using a large stand mixer).
5. Stir melted chocolate and almond meal into egg yolk mixture until well combined.
6. Using rubber spatula, gently fold 1/3 of the egg white mixture into the egg yolk mixture to lighten it. Then very gently fold in remaining egg white mixture until just combined but no white streaks remain.
7. Spread evenly in prepared pan. Bake about 15 minutes, or until it springs back when lightly pressed.
8. Remove from oven and dust top with cocoa powder.
9. Wet a clean dish towel or paper towels and squeeze out as much water as possible. Gently lay wet towel on top of hot cake to cover and let cool completely.



2 T cornstarch
¾ c milk
¾ c sugar
¾ c butter at room temperature
¼ t salt
½ t vanilla extract
½ t almond extract or 2 t amaretto

1. Combine cornstarch, milk, sugar and salt in small saucepan. Cook over medium heat, stirring constantly, until bubbly and thickened. Alternately, microwave mixture for 1 ½ to 2 minutes on high, stirring at 30 second intervals.
2. Refrigerate until completely cooled. (To speed up process, place in freezer for about 15 minutes until chilled but not frozen.)
3. Cream butter until light and fluffy.
4. Beat in cooled cornstarch mixture and flavorings and whip for several minutes until it resembles whipped cream. Use immediately; or refrigerate, let come to room temperature, and rewhip before using.

Step 7: For Both Pie & Log: MARZIPAN IRIS AND LEAVES


4 oz marzipan (sweetened almond paste)
green powdered food coloring
black powdered food coloring
light corn syrup

You'll also need:

waxed paper
rolling pin
small paintbrush
paring knife

Step 8: For Pie: MARZIPAN IRIS


(see completed iris in photo 1)

1. With clean hands, roll about 3 oz of marzipan into a ball. (photo 2)
2. With rolling pin, flatten ball between two sheets of waxed paper. Remove top sheet of waxed paper, and use fingers to taper edges. (photo 3)
3. With dry paintbrush, dust all over with powdered green food coloring. (photo 4)
4. With dry paintbrush, dust edges only with powdered black food coloring, fading black toward the middle. (photo 5)
5. Mix small amount of powdered black food coloring with enough water to make a paste, and use this to paint black pupil in center. (photo 6) Let dry slightly.
6. With clean paintbrush, paint all over with corn syrup to add gloss. (photo 7) Let dry. To speed up process, use a hairdryer set on low heat.



1. With rolling pin, very thinly roll a small amount of remaining marzipan. Cut out leaf shape with paring knife. (photo 1)
3. Use knife to indicate the leaf’s veins. (photo 2)
4. With dry paintbrush, dust all over with powdered green food coloring. (photo 3)
5. Repeat as desired and let dry. For added realism, drape edges of leaves over chopsticks or the edge of a plate before drying. You can also slightly flatten leaf’s edges with fingers before dusting with food coloring.



(see pie layers - cookie crust, ganache, cherry filling, panna cotta, and marzipan - in photo 1)

1. To unmold panna cotta, dip outside of glass bowl in hot water for several seconds.
2. Wipe dry, then run a silicone spatula around edge of panna cotta.
3. Invert panna cotta onto chocolate- and cherry-filled pie plate and carefully remove bowl, shaking gently to release.
4. Gently place marzipan iris in center of pie.
4. Snip a tiny corner from resealable bag filled with reserved cherry “goo.” (photo 2)
5. Use “goo” to pipe blood veins around edges of panna cotta. (photo 3)

Eye pie is finished! (photo 4)



(see log rolled with almond filling and frosted with ganache in photo 1)

1. Remove damp towel from top of cooled cake.
2. Using the parchment paper extending around edge of cake, gently lift and slide cake onto countertop.
3. With sharp knife, cut about a two-inch strip from short end of cake and set aside for now (for the negative sign). The rest of the cake should be a large square now (for the number one).
4. Spread large piece of cake with most of almond filling.
5. Gently roll square of cake into a log, using the parchment liner for support and peeling it away from the cake as you roll.
6. Cut a slice from one end of large roll and reposition on the top left side of roll to make the number one.
7. For the negative sign, cut remaining strip in half, so you’ll end up with two small strips of cake that are about 5”x2” each. (Only one strip is needed – have the other one for a snack!)
8. Spread a strip with remaining almond filling, and roll into a small log to make the negative sign.
9. Arrange the two logs on a serving platter, and frost both smooth with remaining chocolate ganache. (For my serving platter, I covered a 7"x11" piece of sturdy cardboard with parchment paper.)
10. To create bark, use a knife to draw lines in the ganache. (photo 2)
11. Position leaves on your newly finished log negative one. (photo 3)

Log negative one is finished! (photo 4)

Step 12: How to Serve

To serve, cut out a large equals sign from black paper and position between the panna cotta pie and the chocolate log. (photo 1)

Or, if you have access to a large balance, position pie on one side and log on the other. (Be sure to rig the balance so the weight is equal.) (photo 2)

Viola! Serve your i pi = log(-1) concoction with mathematical and culinary pride!

Step 13: Notes ...

These are our brainstorming notes.  :)

Serious Eats Pi Day Pie Contest

Second Prize in the
Serious Eats Pi Day Pie Contest



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    19 Discussions

    i love the logic of thinking up an equation as a reason to bake cake. brilliant!

    INCREDIBLE!!! What an amazing idea! This pie has made me want to 1) eat it and 2) maybe learn a little more about physics ;)

    1 reply

    Are there any pictures of the pie being cut?
    Have you seen "Un Chien Andalou" (An Andalusian Dog)?

    1 reply

    Step 10 shows a photo of the already sliced pie.

    No, I haven't seen "Un Chien Andalou," but I just looked up the section about the calf's eye. How wonderfully icky in reference to a slice of "eye pie"!

    That eye looks really great. I've always been fond of stating this equation as e^(i*pi) + 1 = 0, so you get five hugely important numbers all in one simple equation. Also, I think it is more commonplace to use the natural logarithm, ln, when working with base e. I have seen log used sometimes as the natural log though, and here, the context makes the base obvious. Either way, your clever pie works as a pun for the equation and looks delicious to boot! Great work!

    1 reply