Mix all ingredients at medium speed for 2 minutes. Batter will get thick. Grease and flour two 9-inch cake pans. Distribute batter evenly among cake pans and bake 25-30 minutes, or until toothpick inserted in center comes out clean. Let cool. When cool slice cakes horizontally to form 4 layers.
Pistachio Cream Filling:
Prepare pudding mix using 3 cups of milk according the package directions. Stir in pistachios and cream and refrigerate until ready to use.
Combine chocolate chips, heavy cream and butter and microwave at 70% power for one minute. Stir. Continue microwaving at 10-15 second intervals until smooth and all chocolate is melted. Set aside for 30 minutes.
Assembly your cake layers, filling with pistachio cream filling and leaving the top layer unfrosted. Chill for 30 minutes while ganache is cooling.
Drizzle ganache over entire cake. Top with chopped pistachio nuts. Chill until ready to serve.