My cousin, Katie who is an awesome cook!!, introduced me to this cake. It was so moist and delicious. My husband (who is the pickiest eater on Earth!!!!) devoured this cake. I served it at Thanksgiving this year, and everyone loved it. Of course, we had to wait 4 hours :-) to eat our desserts because we gorged ourselves eating our Thanksgiving meal.
Cook sweet potatoes until soft. Let cool. Peel the potatoes and mash. Place in blender. Add the following: sugar, buttermilk, Bisquick*, melted butter, vanilla extract, eggs, and pudding powder. Blend in blender until smooth. Transfer to a mixer bowl. Add cake mix powder and using an electric mixer, mix until well blended.
Pour into 3 round cake pans that have been sprayed with Baker's Joy* or Pam* Baking spray . (or lightly grease pan and add a little flour)
Bake in oven at 350* for 30-35 minutes. Make sure cake is done by using a tooth pick or other cake tester. Cool on cooling racks.
**Note--cake will be very moist. If too moist, place in freezer while making icing**
While cake rounds are cooling, begin making icing. Place softened butter into an electric mixer bowl and whip until fluffy and white. This will take about 10 minutes. While the butter is whipping in the mixer, place a pot of water on stove and bring the water to simmer. Combine sugar, and egg whites in a medium glass bowl. Set the bowl over the simmering water. Using a whisk, whisk the egg whites constantly until all the sugar is dissolved and the mixture is warm. Remove the whipped butter from the electric mixer. Place the bowl containing the egg white mixture on the electric mixer and beat on high until soft peaks form. Add the whipped butter a little at a time and blend well until all butter has been incorporated. Add softened cream cheese in small amounts until all is incorporated. If desired, add vanilla and mix well. Place icing in refrigerator and chill until icing is spreadable.
Remove icing from refrigerator. Place icing on the bottom cake round (be generous, there is a lot of icing). Place second cake round on top of the frosted cake round and frost it. Place last cake round on top and frost the whole exterior of cake.
**Note this cake is super moist, so if not serving in a few hours, I suggest, placing cake in refrigerator and chill until ready to serve. I keep any leftover cake in the refrigerator**