1. Preheat oven to 350°F.
2. Grease a 2 quart heat-proof bowl (stainless or Pyrex) with shortening and lightly flour. Set aside.
3. Whisk together cocoa and hot water.
4. In a separate bowl, whisk together flour, baking soda, baking powder, and salt.
5. Melt butter with sugar in a saucepan over medium-low heat, stirring to combine. Remove from heat, and pour mixture into a mixing bowl. Beat with an electric hand mixer until mixture has cooled enough to add the eggs without scrambling them.
6. Add eggs, vanilla, and then cocoa mixture. Beat until well combined.
7. Reduce mixer speed and add flour mixture in two batches, alternating with the sour cream.
8. Pour into greased bowl and bake for 60-70 minutes, or until a toothpick tester comes out clean. Let cool slightly.
9. Run a knife around the edge of the cake, then turn out onto a cake stand or serving tray lined with wax paper strips. Let cool completely.
10. Cut the dome of the cake off about 1/3 of the way down from the top.
11. With your fingers, press to make an indentation in the middle of the base of the cake. This will make room for the marshmallow filling without wasting any cake.
You must use a 2 quart (8 cup) bowl for this recipe.
The batter is approx. 4 cups and needs plenty of room to rise while baking.
Wire-pick butterflies can be found in the floral department at most craft stores.