Mounds Bar Cake

Step 1
Preheat oven to 350 degrees F (175 degrees C). Grease and flour a 9×13-inch pan.

Step 2
Melt butter in a large saucepan. Remove saucepan from heat and stir white sugar, eggs, and vanilla extract into the melted butter until thoroughly combined.

Step 3
Mix flour, cocoa powder, salt, and baking powder together in a large mixing bowl; add butter mixture to the flour mixture and stir to form a smooth batter. Pour the batter into the prepared pan.

Step 4
Bake in the preheated oven until a toothpick inserted into the center comes out clean, 25 to 30 minutes. Cool completely.

Step 5
Beat coconut, sweetened condensed milk, and confectioners' sugar together in the bowl of a stand mixer until very thick; spread over the cake in an even layer.

Step 6
Heat prepared frosting in the microwave until the frosting has a pourable consistency, about 75 seconds; pour over the cake and spread into an even layer. Refrigerate cake until the frosting is set, at least 15 minutes.