Melt the butter in a microwave safe mug.
Add the egg and beat well.
Stir in the coffee and whiskey.
Add the Keto Chow, coconut flour, erythritol, and baking powder and mix well.
Microwave for 60-90 seconds. The cake should rise to the top of the mug, begin to shrink from the sides and be dry in the center.
Allow the mug to cool in the microwave for one minute before removing it.
Gently loosen the cake in the mug and transfer it to a small plate to cool.
To make the topping, place the heavy cream in a small bowl, sprinkle the Keto Chow and erythritol over it and add the 1/2 teaspoon of whiskey, if using.
Whip the cream with a whisk or handheld blender until it’s doubled in volume and holds a stiff peak.
Top the mug cake with the whipped cream and enjoy.