After tweaking this recipe for awhile, I made this version for Easter. Everyone was telling me how good it was but when my 15 year old son tasted it, he proclaimed, "Mom, you finally got it!" I then knew not to change it anymore.
Preheat oven to 350 degrees F and lightly grease two 9 inch round cake pans.
In a large bowl, beat cake mix, dry pudding mix, pudding cup, eggs, sour cream, vegetable oil and water with an electric mixer on low speed until just moistened, scraping sides frequently. Then beat on medium speed for 2 minutes.
Stir in chopped chocolate and toffee chips. Spoon evenly into prepared pans.
Bake 50 minutes or until a toothpick inserted near the center comes out clean. Cool in pans for 10 minutes on a wire rack. Loosen cakes from the side of pans with a spatula or knife. Invert cakes onto the rack; gently remove the pans. Cool completely on the wire rack.
While cake is cooling, beat frosting, pudding cup and vanilla with an electric mixer until well mixed and fluffy, scraping sides frequently. Fold in whipped topping until well mixed.
Place 1 of the cake layers on a serving plate. Spread top of the layer with frosting (don't be stingy, you'll have plenty of frosting). Place other layer on top. Frost the rest of the cake.