Rainbow Explosion Cake

Directions for Cake
1. Preheat your oven to 350°F (175°C) and put the oven rack in the middle of the oven. If you are using a convection oven, set it to 325°F (165°C).
2. Combine the flour, baking powder, and salt in a large bowl and whisk until they are really mixed together. You have to mix all the dry ingredients together first, so that there are no clumps in your batter, which will create white spots .Set aside.
3. In a separate bowl, use an electric mixer on medium speed to blend the butter and sugar together, until they become fluffy. Make sure to scrape the sides of the bowl with a spatula so it’s all mixed in from the sides.
4. Add the eggs, one at a time, to the butter-sugar mixture, with the mixer on medium speed. Again, make sure to scrape the sides of the bowl. Add the vanilla to the milk and set it aside.
5. Mix about one-third of your dry ingredients into the butter-sugar-egg mixture, then blend in half of the milk, always mixing on medium speed.
6. Mix in the second third of the dry ingredients, then the remaining milk mixture.
7. Stop the mixer for a few seconds and use a spatula to push down anything sticking to the sides of the bowl as you go, then mix in the last of the flour mixture. Make sure it’s all mixed in from the sides and everything is smooth. You don’t want any lumps, but don’t overmix it—stop the mixer as soon as the batter is smooth.
8. Divide the batter evenly into six portions. They don’t have to be exactly identical, but you want them to be close: You can use any small bowls that are all the same size: Just slowly pour the batter into each of the bowls a little at a time until they are all at the same height. (It’s about 1 cup/250 g of batter per bowl.)
9. Color the batter individually in rainbow colors: We use purple, blue, green, yellow, orange, and pink for our six-layer cakes. Start with a tiny drop of food coloring, stir it in completely, then add more until it is your desired color. (The baked cake will come out pretty close to what you see—the outside will be a little brown, but that gets covered with frosting.) See Tools & Tips for Frosting Cakes on page 26 for more on food dye.
10. Spray six 6-inch (15-cm) round baking pans with cooking spray, then pour the colored batter into the greased pans.
11. Bake the cakes two at a time for 8 minutes without opening the oven door. Then rotate each pan so the front faces the back. Bake for another 8 minutes, or until a toothpick comes out clean when you insert it into the middle of the cake. (Cakes are very sensitive. The less you open your oven, the better your cake will come out! I don’t know exactly why, but I know it.)
12. Let the cakes cool in the pans for 5 to 10 minutes. (When they’re warm, they’re really fragile, and that’s when they tend to break.) Then flip them over onto a baking sheet or cooling rack and let them cool completely before you frost them.
Note on Cake:
If you don’t have 6-inch (15-cm) cake pans, you can also make a larger rainbow cake with six 8-inch (20-cm) pans. Just double the ingredients, and increase the baking time to ten minutes per side. A general rule for scaling this recipe is that if you want to make more or less of this cake, scale it up or down in thirds, because there are three eggs and those can’t be easily divided! At Flour Shop we make four sizes of cakes: the mini (3-inch/7.5-cm), the midi (6 inch/15-cm), the maxi (8-inch/20-cm), and the mega (10-inch/25-cm), which we named after skirt lengths. Usually, one mini serves 4, one midi serves 15, one maxi serves 25, and one mega serves 50.
Directions for Frosting
1. Use an electric mixer on medium speed to blend the butter until it is smooth. Add the cream cheese and blend it together until there are no lumps. Then add the vanilla. Stop the mixer and use a spatula to push down anything sticking to the sides of the bowl, making sure it’s all mixed in from the sides and everything is smooth.
2. Mix in the powdered sugar a little bit at a time on the lowest speed—otherwise it will fly everywhere! Use the spatula to push down anything sticking to the sides of the bowl, making sure it’s all mixed in from the sides and everything is smooth.
3. Use right away. Technically the frosting will last at least a week in the refrigerator, but fresh frosting is key! It tastes and feels so much better.
Note on Frosting
Makes 6 cups (3 ½ pounds/1.6 kg) of frosting. This will make plenty of frosting for a Rainbow Explosion Cake and most of the other cakes in this book, plus a little extra in case you need to cover up mistakes. In some cases, we note where you may need less, and you can easily cut this recipe in half or even quarter it.
Directions for Assembly
1. Once your cakes are baked and completely cool, lay them out with the tops facing up.
2. Use a 2-inch (5-cm) round cookie cutter to cut the center out of every cake but the top one. Never cut a hole in your top layer of cake! In this particular case, the top is the pink layer, but you can choose whichever color you want your top to be.
TIP: Some of the cake might stay on the ring, so wipe it in between each cut so you don’t transfer one cake color to the others, and you get a nice, clean center after you cut it open. Just be very, very careful to try to get the center every time, or else your layers won’t line up when you stack them all together. I like to cut them from above, because when you look at it from the side, you get a slightly different perspective.
3. Before you assemble your cake, you’ll need a base to build it on. You can buy disposable round cake-decorating boards, or you can use a plate, a cake stand, or a flat platter—whatever you use, just make sure the base is a little bigger than your cake. My rule of thumb is that the base should be about 2 inches bigger than the cake pan.
4. You start to build a six-layer cake by putting a small ring of frosting directly on top of the board in roughly the same shape as the cake ring. This is so that the cake really sticks to the base and isn’t sliding around while you’re working. I always frost cake layers with a piping bag, so it is easy to draw a ring.
5. Put the first layer of cake directly on top of the frosting. In this case, the bottom layer is purple.
6. Cover the top of the cake with an even layer of frosting. Using a piping bag, make sure to squeeze on the same amount of frosting for every layer: You just add on the same number of rings every time. I usually make three thick rings around the top of each cake, leaving a little room around the hole: The secret trick is to start by making the first ring around the hole, then moving out. You don’t want to get frosting in the hole, or your sprinkles explosion will stick to the frosting.
7. Add the second layer of cake. Eyeball it from the top after you do, to make sure the holes line up. It’s easier to adjust as you go, rather than to fix a tilting six-layer cake at the end. Add another layer of frosting and repeat until you reach layer 5.
8. Now, pour the sprinkles down into the center of the hole! A measuring cup with a spout works perfectly. You’ll need about 1 ¾ cups (1 pound/455 g) of sprinkles to fill this cake. Stop and pat down the sprinkles to the height of the cake/frosting.
9. Now add the sixth and final layer of the rainbow!
10. Flip it upside-down first, so you have a flat surface to frost on the top of the cake. This is my secret way to make a straight cake, rather than trimming off any cake.
11. Apply a crumb coat and refrigerate
12. After the crumb coat is in place, cover the cake in a final layer of frosting. Of course, if you are making this to share right away and your cake doesn’t need a few minutes of chilling time, you can simply cover the cake in frosting in just one step. Either way, the final coat on this cake doesn’t have to be too thick, because we’re going to cover the cake in sprinkles. Our second layer of frosting is really for the sprinkles, so they’ll stick.
13. Cup hands and scoop up a few sprinkles, and then start moving hands up along the side of the cake, working from the bottom to the top. Drop the sprinkles against the cake as you go, and eventually they start to stick—just work your way around and around the cake until everything is covered.
14. Once you’ve sprinkled it, you can—you should—enjoy it right away, but you can store it in the fridge for a few hours or overnight.
Note on Assembly: To cover the outside of 1 rainbow cake or 3 mini cakes in sprinkles, you will need: ½ pound sprinkles = 225 g = about 1 cup / To fill the inside of 1 rainbow cake or 3 mini cakes with mixed sprinkles, you will need: 1 pound mixed sprinkles = 455 g = about 1 ¾ cups (keep in mind, these don’t have to be sprinkles; it can just be 1 ¾ cups of candy!)

Get more information about this episode >>