This cake is simple and easy to put together and looks lovely. I have made it for several office parties and it is always a hit. I found this recipe on taste of home but it had almonds and I like pudding in the mix of my cakes to make it moister...so I altered it to fit my tastes..
Prepare cake according to package directions in two greased and floured 9 inch cake pans. Cool completely and cut both of the layers in half horizontally to make four layers total. Place one layer on a serving plate. In a small saucepan, melt chocolate and butter. Stir till smooth. Stir in walnuts. It will be thin consistency. Spread 1/2 of the chocolate on the 1st cake layer. Top with another layer of cake. Spread half the cool whip on top. Top with another cake layer. Spread the remaining chocolate on this layer and top with last cake layer. Spread with remaining cool whip.
Sprinkle with chocolate curls. Chill at least one hour before serving. Refrigerate left over cake.