To make the cake

1. Preheat oven to 350°F (176°C) and prepare an 8 inch round cake pan (or springform pan) with parchment paper in the bottom and non stick spray around the sides.
2. In a large mixing bowl, cream sugars, butter and peanut butter until light in color and fluffy, about 3-4 minutes.
3. Add sour cream and vanilla extract and mix until well combined.
4. Add egg whites in two batches, mixing until well combined after each. Scrape down the sides of the bowl as needed to be sure all ingredients are well incorporated.
5. Combine the dry ingredients in another bowl, then combine milk and water in another bowl.
6. Add half of the dry ingredients to the batter and mix until well combined. Add the milk mixture and mix until well combined. Add remaining dry ingredients and mix until well combined. Scrape down the sides of the bowl as needed to be sure all ingredients are well incorporated.
7. Add the cake batter to prepared cake pan. Bake for 38 minutes, or until a toothpick inserted comes out with a few crumbs.
8. Remove cake from oven and allow to cool for 2-3 minutes, then remove to cooling rack to finish cooling.

For the ice cream filling

1. When the cake has finished cooling, put the ice cream in the fridge for about an hour to soften.
2. Once the cake is cool, set up your 8-inch cake pan (or springform pan) for layering. If not using a springform pan, you can put some plastic wrap in the bottom of the pan and up the sides and use it to lift the cake out of the pan when it’s done. Put a cardboard cake circle in the bottom of the pan. Line the sides of the pan with parchment paper. The parchment paper should stick up above the top edge of the pan (see example).
   NOTE: You should be using the same 8-inch pan you used for the cake. Not all 8-inch pans are exactly the same size. Your cake needs to fit in this pan. Alternatively, you could use a clear cake collar.
3. Cut the dome off of the top of the cake layer, then place the cake layer into the bottom of the pan.
4. To make the filling, add 3 oz of chocolate chips to a small bowl.
5. Heat the heavy whipping cream and corn syrup until it begins to boil, then pour it over the chocolate chips. Allow the mixture to sit for 3-4 minutes, then whisk until smooth.
6. Add the chopped waffle cone pieces and stir to combine. Spread the mixture evenly over the top of the peanut butter cake.
7. Top the waffle cone pieces with the ice cream and spread the ice cream into an even layer.
8. Freeze the cake until firm, 5-6 hours.

To frost and decorate

1. To prepare the whipped cream frosting, add the heavy whipping cream, powdered sugar, peanut butter and vanilla extract to a large mixer bowl. Whip on high speed until stiff peaks form.
2. Remove the frozen cake from the pan and quickly frost the outside with the whipped cream. The ice cream will melt, so pop it back in the freezer as needed and when you’re done.
3. To make the chocolate ganache topping, heat the heavy whipping cream until it begins to boil, then pour it over the chocolate chips. Allow the mixture to sit for 3-4 minutes, then whisk until smooth.
4. Drizzle the ganache around the edge of the cake, then top with chopped waffle cone pieces and a coupe mini ice cream cones (see my tips on making a chocolate drip cake). Freeze until ready to serve.