Preheat the oven to 350°F (175°C) and line the bottoms of two 9-inch round cake pans with parchment paper, then grease the sides.

In a medium bowl, sift together the flour, baking powder, and salt and set aside.

In a large bowl, beat 1/2 cup softened butter and the granulated sugar on medium speed for 2 to 3 minutes until pale and fluffy.

Add the eggs one at a time, beating well after each addition, then mix in the vanilla extract.

Alternate adding the sifted dry ingredients and the whole milk in three additions, beginning and ending with the flour mixture, mixing each addition on low speed until just combined.

Divide the batter evenly between the prepared pans and smooth the tops with an offset spatula.

Bake for 28 to 32 minutes or until a toothpick inserted in the center comes out clean, then remove from the oven.

Allow the cakes to cool in the pans for 10 minutes, then turn out onto a cooling rack and cool completely, about 1 hour.

While the cakes cool, prepare the frosting by beating 1 cup softened butter on medium speed for 1 minute until creamy.

Gradually add the powdered sugar, one cup at a time, mixing on low speed, then pour in the heavy cream and vanilla extract and beat on medium speed until light and fluffy.

Fold in the crushed Butterfinger pieces, reserving about 1/2 cup for decorating the cake.

Place one cake layer on a serving plate, spread about 1 cup of frosting over the top, then top with the second layer and frost the top and sides of the cake.

Sprinkle the reserved crushed Butterfinger pieces over the top and around the sides of the cake, then chill for 30 minutes before serving.