1. Preheat oven to 350F and grease or line a cupcake pan.
2. In a stand mixer, cream together the butter, eggs, sour cream, oil, and sugar.
3. In a separate bowl combine the dry ingredients.
4. With the mixer on low, slowly add the dry ingredients to the wet. Turn the mixer to med-high and whip together. The batter will be very thick.
5. Fill cupcake pans  to 3/4 of the way full and smooth out the tops with a spoon.
6. Bake for 20 minutes, or until a toothpick inserted into the center comes out clean.
7. Allow to cool completely before moving to the next step.

The Filling

1.  Once the cupcakes are completely cool, remove them from the pan or paper liner. Using a small pairing knife, cut out a small hole on the bottom and hollow out a portion of the inside. KEEP the cake pieces you remove, you will need them in a minute.
2. Spoon or pipe marshmallow cream into the holes, taking care not to over fill them.
3. Mash the removed cake pieces (they should be moist enough to form a dough) into a circle that will cover the hole on the bottom of your cake, covering the cream. This doesn't need to be pretty, you are covering everything with chocolate soon.

The Ganache

1. Place the heavy cream in a microwaveable bowl and heat on high for 1 minute. Whisk in chocolate chips and let them melt together to form the ganache.
2. Spoon the chocolate ganache over your filled cakes, using the spoon to work the chocolate around the cakes completely.
3. Allow the ganache to set up slightly (or put into the freezer for 15-20 minutes) before serving.