chocolate mocha heath bar cake

I made up this cake for my Heath-loving mom to celebrate Mother's Day. It was my first time using this recipe for yellow cake, and I was not entirely satisfied with it. I was looking for a moister, more tender cake. I plan on trying another recipe next time. I loved the way the mocha frosting turned out, and I think it would be great to frost a chocolate layer cake.

Chocolate Mocha Heath Bar Cake

For cake:
via Smitten Kitchen

4 c. plus 2 tbs. cake flour
2 tsp. baking powder
1 1/2 tsp. baking soda
1 tsp. salt
2 sticks butter, softened
2 c. sugar
2 tsp. vanilla
4 large eggs, room temperature
2 c. buttermilk, well-shaken

Preheat oven to 350 degrees. Butter three 9-inch round cake pans and line with parchment paper.

Combine flour, baking powder, baking soda, and salt in medium bowl. Beat butter and sugar in a large bowl until pale and fluffy. Add vanilla. Add eggs, 1 at a time, until well-combined. At low speed, beat in buttermilk. Add flour mixture in three batches, mixing until each addition is just incorporated.

Divide batter amongst pans. Bake until golden, about 35 minutes. Invert on rack and cool completely.

For chocolate buttercream filling:

1 1/2 sticks butter, softened
4 c. powdered sugar
1 tsp. vanilla
1/2 c. semisweet chocolate chips, melted and cooled
1/2 c. cocoa powder
4 Heath Bars, chopped

Beat butter until fluffy. Add in sugar, vanilla, chocolate, and cocoa powder. Stir in chopped Health Bars.

For mocha buttercream:

1 1/2 sticks butter, softened
4 c. powdered sugar
1 tsp. vanilla
1/4 c. semisweet chocolate chips, melted
1 tbs. instant espresso

Beat butter until fluffy. While chocolate is still warm, mix in instant espresso, to dissolve. Beat sugar, vanilla, and chocolate-espresso mixture into butter.

Layer cakes with chocolate-Heath filling. Frost top and sides of cake with mocha buttercream.