• Preheat oven to 350°. Grease and flour two 9x2-inch round cake pans.
• Beat cake mix, mayonnaise, water, and eggs until mixed, then beat with an electric mixer for 4 minutes. Pour into the pans, dividing evenly.
• Bake 25-30 minutes or until toothpick inserted in centers comes out clean.
• Let cool on a wire rack 10 minutes. Remove cakes from pans and cool completely.
• Pick the cake with the least attractive top and trim it so that you have a flat surface to put the cream on. You'll have some scraps for sampling, decorating or making cake balls. Are they still a thing?
• Spread Bavarian Cream on the trimmed surface and cap with the other layer. Chill for about an hour or until cake is cold, then cover with the chocolate ganache.

Bavarian Cream Filling

• The filling needs some time to thicken, so you may want to start making it when you take the cake out of the oven. It can sit in the bowl and thicken while the cake cools.
• Whisk together pudding mix and milk. I usually just throw it in the stand mixer bowl and let the whisk attachment handle it. Mixture will start out thin and thicken just slightly. Fold in whipped topping. Put the bowl in the refrigerator and chill for about 30 minutes before putting it on the cooled cake. It tends to thicken even more as it sits.

Ganache

• Put the cream and corn syrup in a 2 cup measure and heat in the microwave just until it begins to boil (that's less than a minute in my microwave). Add the chocolate and let stand for 5 minutes to soften. Stir until smooth. Let stand until you feel it is thick enough to pour over the cake (it might be thick immediately), then pour over cold cake. You may need to use a spoon to gently spread in a circular motion to coax chocolate down the side.