Preheat oven to 350°F. Grease 3 9-inch round cake pans with butter or nonstick spray. Set aside.
Add the flour, sugars, cocoa powder, baking soda, baking powder, and salt to a large bowl and whisk until combined.
3½ cups all-purpose flour, 2 cups granulated sugar, 1 cup brown sugar, 1½ cups unsweetened cocoa powder, 1 tablespoon baking soda, 2 teaspoons baking powder, 1 teaspoon kosher salt
In a separate bowl, whisk the eggs, milk, Greek yogurt, water, vanilla extract, and melted butter together.
5 large eggs, 2 cups milk, 1 cup plain Greek yogurt, 1 cup water, 1 tablespoon pure vanilla extract, ¾ cup unsalted butter
Add the wet ingredients to the dry ingredients and mix with a hand mixer until just combined.
Fold in the chocolate chips.
¾ cup chocolate chips
Pour the batter evenly among the 3 cake pans.
Bake for 35 minutes or until a toothpick inserted in the center of the cake comes out clean. Let the cake cool for at least 10 minutes.
While the cake is baking and cooling, make the frosting. Start by creaming the butter until smooth with a hand mixer.
2 cups unsalted butter
Sift in the powdered sugar and cocoa powder. Mix until well incorporated.
4 cups powdered sugar, 1 cup unsweetened cocoa powder
Add in the vanilla extract, salt, and heavy cream and mix again until the frosting reaches a smooth and creamy consistency with stiff peaks.
2 teaspoons pure vanilla extract, ½ teaspoon kosher salt, ½ cup heavy cream
Transfer 1 cake layer to a cake stand and add a layer of frosting on top. Add on the 2nd cake layer, another layer of frosting, and the 3rd layer of cake.
Frost the entire exterior of the cake.
Pipe designs on the top of the cake if desired. Add chocolate chips and sprinkles to the top and sides of the cake, if desired.
Chocolate chips, Chocolate sprinkles