The Science of Molecular Gastronomy: Galaxy Mirror Cake

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About: I am a recent physics grad who has a passion for everything science related!

So you want to make a galaxy { cake ;) }, do you? Well, I'm here to help and explain the science behind what makes this astronomy-themed cake so sweet (pun intended).

Baking can be intimidating: It's so precise and mathematical. That's why they call it a science, while is cooking an art ... right? Well, actually, baking can definitely be an art — and a fun one, at that. Essentially, gelatin, sugar, and water are at the heart of this recipe, but mirror glazes can have many variations to add flavor and color. The glaze can be applied to an array of desserts finished with a cream—you wouldn’t want to apply directly to an unfrosted cake, because it would absorb the glaze like a sponge. However, on a frosted cake, the glaze will completely enrobe the whole shape of the dessert when you pour it, and set up on top.

"Gloss" is an optical property which tells us how well a surface can reflect light in a specular (mirror-like) direction. It is an important characteristic that's used to describe the visual appearance of an object. The factors that affect gloss are the refractive index of the material, the angle of incident (incoming) light, and the topography of the surface (ie. the smoothness/roughness of the surface).

The refractive index of gelatin (used to make the glaze for this cake) is approximately 1.51-1.54.

Temperature also plays a part in giving our glaze its glossy appearance: Bringing the mixture down from boiling to a lower temperature, 43˚ to 48˚ (Celsius), is the key to getting that shine when you pour the glaze; it then sets when it cools at 30˚.

List of items you will need:

* (2) 6” Round Confetti/Vanilla Cakes

* (8) Ounces White Chocolate: http://amzn.to/2aQUHQ6

* (1) Cup Sugar: http://amzn.to/2b4f4sW

* (1/2) Cup Cold Water

* (1/4) Cup Water

* (1/2) Cup Light Corn Syrup: http://amzn.to/2b4f4sW

* (1/2) Cup Sweetened Condensed Milk: http://amzn.to/2b4f4sW

* (5) Teaspoons Powdered Gelatin: http://amzn.to/2b4f4sW

* (1) Container Vanilla Buttercream Frosting: http://amzn.to/2b4f4sW

* (1) Container Black Food Coloring: http://amzn.to/2b4f4sW

* (1) Container White Food Coloring: http://amzn.to/2b4f4sW

* (1) Container Navy Blue Food Coloring: http://amzn.to/2b4f4sW

* (1) Container Electric Blue Food Coloring: http://amzn.to/2b4f4sW

* (1) Container Purple Food Coloring: http://amzn.to/2b4f4sW

* (1) Container Pink Food Coloring: http://amzn.to/2b4f4sW

* (1) Container Black Disco Dust: http://amzn.to/2b4f4sW

Step 1: Getting Started

First off, you need to make the base of your galaxy by making your cake(s). I suggest using confetti cake mix, because it's delicious, but also because the little flecks of confetti can act as stars on the inside of your cake. You want to combine the cake mix, three eggs, and vegetable oil in a bowl, and stir until homogenous (completely mixed together).Next, butter your two six inch baking pans, and then pour your mixture into the pans as evenly as possible. Preheat your over to 350 degrees Celsius, and then bake for approximately 28 mins (until golden brown, as in the pictures).

Step 2: Frost That Base! (Hint: As Smooooothly As Possible!)

Place your two 6 inch cakes in the fridge for about thirty minutes to set. Once complete, remove the two cakes from the fridge and cut off the "tops" of both cakes so that they are level on both their top and bottom halves. Ice the freshly cut faces of both cake pieces, stick together (one on top of the other), and then place on a circular (preferably rotating) object, on top of a large baking sheet. Finish icing the outside of your cake using a flat knife edge to smooth out the surface as much as possible.

Step 3: How to Make a Glossy Galaxy (Glaze)

Mix the gelatin in a bowl with 1/4 cup of water, and set aside to let it bloom while you begin the glaze. Over a medium heat, stir together the sugar, water, and sweetened condensed milk. Stir occasionally, until the mixture begins to bubble. At this point, pour in the gelatin, and stir until fully dissolved. Remember to turn off the stovetop.

Step 4: A Little Chocolate Never Hurt Anybody...

Gently pour in the white chocolate chips. Stir slowly with an electric hand mixer, until all the white chocolate has melted. Pour through a sieve into a large bowl, then divide the glaze evenly between five bowls. Leave one uncolored, and color the other bowls black, purple, blue, and pink. Once colored, pour half of the black into the large bowl.

Step 5: Final Step: "Painting" the Galaxy

Use the food colors to color the other bowls green, purple, blue, and pink. Once colored, pour about 2/3 of the purple and pink glazes into the blue glaze, and then slowly pour over top of the cake in a swirling motion. Drizzle some small drops of the white glaze and/or black sprinkles on top of the colors to act as starts (this part is optional). I placed a 4-inch cake pan underneath my cake and covered it with baking paper before slowly pouring the glaze on the cake (to make for easier clean up). Once I made sure my glazes were 50 degrees Celsius (temperature required to have the glaze pour smoothly), I began pouring the glaze over the edges, then worked my way into the center. Once I had fully covered the cake, I sprinkle a line of edible glitter over the top. I let it continue to drip for about 10 minutes, then placed the cake in the fridge to set.

That's it! You have created an amazing galactic treat, and executed some pretty neat molecular gastronomy!

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    5 Discussions

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    JoyceL53

    6 months ago

    Very cool. Perfect activity to do with the class to celebrate end of the school term.

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    PamelaR70

    6 months ago on Step 2

    These are the best instructions for "Galaxy Cake" I have ever seen!

    Well Done! I loved you explained the science behind it!!

    1 reply