Candy Snack Cake

1 cup butter, softened
1 cup sugar
4 large eggs
1 teaspoon vanilla extract
1 cup all-purpose flour
1/4 cup unsweetened cocoa powder
1/2 teaspoon baking powder
1/4 teaspoon salt
Chocolate Frosting, recipe follows
Whipped cream, for topping, optional
Directions
Preheat oven to 350 degrees F. Line 9-inch baking pan with heavy-duty aluminum foil.
In a large bowl, combine butter and sugar. Beat at medium speed with an electric mixer until fluffy. Add eggs, 1 at a time, beating well after each addition. Beat in vanilla extract.
In a small bowl, combine flour, cocoa, baking powder, and salt. Gradually add to butter mixture, beating until combined. Spoon batter into prepared pan.
Bake for 22 minutes or until a wooden pick inserted in center comes out clean. Spread chocolate frosting over hot cake. Let cool completely. Cut into squares and serve with whipped cream, if desired.

Chocolate Frosting:
1/4 cup butter
2 tablespoons unsweetened cocoa powder
3 tablespoons buttermilk
2 cups confectioners' sugar
3 (2.07-ounce) candy bars cut into 1/2-inch pieces (recommended: Snickers)
In a medium saucepan, melt butter over medium-low heat. Add cocoa, buttermilk and 1 cup confectioners' sugar. Stir in candy bars and allow to melt. Stir in remaining confectioners' sugar and immediately spread over hot cake.