Preheat your oven to 350 and prep your cupcake pan well for nonstick.
Place the brownie mix in a mixing bowl and use a fork or a whisk to break up any lumps. Then beat in the oil, water, and the egg until just combined.
Use a spoon to fill the cupcake liners three fourths of the way full. Bake the cupcakes for 18-20 minutes or until the sides of the cupcakes are set and the center is still somewhat soft.
Carefully remove the cupcakes from the oven and use the backside of a measuring spoon to make an indent or well in the center of each of the cupcakes to hold the filling. Allow the cupcakes to cool in the pan for five minutes before transferring to a cooling rack to completely cool. In a stand mixers outfitter with a whisk or beater attachment, beat the heavy whipping cream, cocoa powder, and the sugar on medium high until stiff peaks form.
Use a teaspoon to evenly place a spoonful or two into the center well that you created in each of the cupcakes. Then place the the cupcakes on a rimmed tray or baking dish and refrigerate them until set ( few hours).
Remove the cupcakes from your refrigerator, use a spoon to add the cherry pie filling on top of the mousse in each of the cupcakes.
Top each of the cupcakes with whipped cream and serve.