If you plan to bake the cakes, preheat the oven to 350F
Mix together all dry ingedients (flour, cocoa powder, baking powder, salt, and sweetener)
Combine all the remaining ingredients in another bowl
Add the wet to the dry and completely combine
If baking, dole out two cakes-worth into a greased muffin-top pan. Bake at 350 for 15 minutes or until a toothpick stuck in the center comes out clean
If microwaving, spoon into a five or six inch ramekin, and microwave for one minute. Alternatively, you could pour 1/2 onto a plate and nuke for 30 seconds – then repeat with the second half
Remove and let stand for just a couple minutes
If baking, remove carefully with a rubber spatula. If nuking, remove from the ramekin. Set on a wire-rack to cool for at least 10 minutes
If baking, use a knife to carefully remove the bottom portion, leaving only the cap. Set aside
If nuking in a ramekin, slice the cake in half lengthwise
To make the filling, whip the cream in a chilled stainless steel bowl until almost butter – but not quite. Add the sweetener and vanilla and mix thoroughly
Assemble the whoopie pie by layering the filling between the cakes