Glow-in-the-dark cake

Ingredients:

Cake

• Cooking spray to spray the molds
• All-purpose flour to dust the pans
• 2 x 450g packages of white sponge cake mix (+ any additional ingredients needed)
• 5 drops of deep green gel food coloring (electric green)
• 5 drops deep pink gel food coloring
• 5 drops lemon yellow gel food coloring

Butter cream

• 450 g unsalted butter at room temperature
• A pinch of fine salt
• 8 cups sifted powdered sugar
• 1 tbsp vanilla extract
• 2-4 tablespoons of milk

Glaze

• 2 packages of 280g marshmallows
• 4 tablespoons unsalted butter
• 1 and 1/4 cups tonic water (with quinine) at room temperature
• 3 drops deep green gel food coloring (electric green)
• 3 drops deep pink gel food coloring
• Special equipment: 4 round cake pans with a diameter of 20 cm; cake stand; rotating cake stand

Preparation:

1. Preheat oven to 350°F (175°C). Spray four 8-inch round cake pans with cooking spray and dust with flour, shaking out any excess. If you don't have four pans, prepare one package of cake mix at a time and use half the food coloring in each batch.
2. Cake:
   
   Mix the crust dough according to package directions. Divide the dough evenly among 3 bowls. Add green food coloring to one bowl, pink to another, and yellow to a third. Tie-dye the dough by dropping the dough ¼ cup at a time into the prepared pans, alternating colors. Run a toothpick through the dough to create a marbled pattern. Tap the pan on the counter to release any air bubbles, and bake, rotating the pans halfway through, until a tester inserted into the center comes out clean, 25 to 28 minutes. Cool on a wire rack for 10 minutes, then remove from the pans and cool completely.
3. Butter cream:
   
   In a large bowl, beat the butter and salt with a mixer on medium-high speed until smooth and light, about 1 minute. Add the powdered sugar and mix on low speed until fully incorporated, then increase the speed to medium and beat until fluffy, 1-2 minutes. Beat in the vanilla extract, then the milk, 1 tablespoon at a time, until the frosting is a smooth paste.
4. Trim the domed tops off the cake layers to flatten them. Spread about 0.5 cups of frosting on one layer. Place another layer on top and frost again. Repeat with the third layer, then add the fourth layer upside down. Cover the cake with a very thin layer of frosting to smooth out any crumbs, and refrigerate for about 15 minutes to set.
5. Place the cake on a cake stand and spread the remaining frosting evenly over it. Freeze the cake for at least 4 hours or overnight.
6. Glaze:
   
   Combine the marshmallows and butter in a microwave-safe bowl. Microwave on high in 30-second intervals, stirring, until smooth and melted, 1 to 2 minutes. Slowly whisk the tonic into the glaze; it should be pourable but still coat the back of a spatula. Divide the glaze evenly among 3 bowls. Stir in food coloring: green in one bowl, pink in another, and leave the third bowl white.
7. Place the cake on a rotating cake stand set on a baking sheet, or place the cake on a tall can (such as a soup can) set on the baking sheet. Pour the glaze over the cake in a circle, starting at the edges and working toward the center, alternating colors and making sure the glaze covers the entire cake. Let the glaze drip for about 15 minutes, then refrigerate the cake to set.