How to Make It
Prepare the Cake Layers: Preheat oven to 350°F. Combine candy bars and 1/2 cup butter in a small saucepan; cook over medium heat, whisking frequently, until melted and smooth, about 3 minutes. Remove from heat and cool 5 minutes.
Beat granulated sugar and remaining 1/2 cup butter with an electric mixer on medium speed until light and fluffy, about 3 minutes. Add eggs 1 at a time, beating until blended after each addition. Whisk together flour, salt, and baking soda. Gradually add flour mixture, alternately with buttermilk, beginning and ending with flour mixture. Beat on low speed just until blended after each addition. Add melted candy mixture and vanilla; beat on low speed just until blended. Divide batter among 3 greased (with shortening) and floured 9-inch round pans.
Bake in preheated oven until a wooden pick inserted in center comes out clean, 25 to 30 minutes. Cool in pans on a wire rack 10 minutes. Remove from pan to wire rack; cool completely, about 30 minutes.
Prepare the Frosting: Microwave chocolate in a microwave-safe bowl on HIGH 1 minute or until melted and smooth, stirring after 30 seconds. Cool 5 minutes.
Beat butter and powdered sugar with an electric mixer on low speed until smooth. Add malt drink mix, vanilla, and salt; beat on low speed 2 minutes. Add melted chocolate and beat on low speed 2 minutes. Add 3 tablespoons cream and beat on medium speed until smooth and spreadable, adding an additional tablespoon of cream if needed to reach desired consistency.
Spread frosting between layers and on top and sides of cake. Garnish with candy bars as desired.