Preheat oven to 350°F.
Cut parchment paper to fit the bottom of two 8-inch round cake pans. Spray the pans with cooking spray, line the bottoms with parchment, then spray the parchment as well.
cooking spray
In the bowl of a stand mixer or large mixing bowl, whisk together the flour, sugar, baking powder, and salt.
2-1/4 cup all-purpose flour, 1-1/2 cups granulated sugar, 3-1/2 tsps. baking powder, 1 tsp. table salt
Measure 1¼ cups of milk in a glass measuring cup, then add enough vegetable oil to bring the total liquid to 1⅓ cups. (Be precise here—they’re close measurements.)
1-1/4 cups whole milk, vegetable oil
Add the milk mixture, butter, and vanilla to the dry ingredients and beat on medium-high speed for 2 minutes. Add the eggs and beat for another 2 minutes. Divide the batter evenly between the prepared pans.
8 tbsps. butter, 1 tbsp. vanilla extract, 3 large eggs
Bake for 25–30 minutes, or until a toothpick inserted in the center comes out clean. Cool the cakes in the pans on wire racks for 20 minutes. Then run a knife around the edges to loosen, remove the cakes from the pans, and cool completely.
To make the frosting, in a large (10–12") saucepan, whisk together the sugar, cornstarch, cocoa, 1 tablespoon of butter, and salt. Pour in 1½ cups of boiling water and start whisking.
1-1/2 cups granulated sugar, 1/4 cup + 2 tbsps. cornstarch, 7 tbsps. unsweetened cocoa powder, 7 tbsps. butter, 3/4 tsp. table salt, 1-1/2 cups boiling water
Turn the heat to medium-low and continue to whisk until the mixture thickens, about 3–4 minutes. Whisk in the remaining 6 tablespoons of butter and the vanilla.
Remove from heat and let the frosting cool completely—it will continue to thicken as it cools. I like to chill it in the fridge to help it firm up until it's a spreadable consistency.
Once the cakes are cool, level the tops so they stack evenly. Spread the frosting between the layers, then frost the top and sides.
To decorate, arrange the Peeps (without separating them) around the edge of the cake, curving slightly to create sunflower petals. Fill the center with chocolate chips to look like sunflower seeds.
20 yellow chick Peeps, 1-1/2 cups semi-sweet chocolate chips