In a mug, combine all your cake ingredients and mix thoroughly until everything is well incorporated. You can do this in a blender or food processor too. Microwave on high heat for 90 seconds. Take your cake out of the mug and let it completely cool down. Slice your cake to make 2 layers and place them somewhere cool.
In a bowl, add cream cheese, erythritol and vanilla extract. Using an electric hand mixer whip all the ingredients together until you get a soft creamy mixture. Add your whipping cream and mix again for 5 minutes. Set aside.
Take one layer of the cake and scoop on top of it one heaped tbsp of your cream cheese frosting. Gently place the top layer on it and scoop on top of it another heaped tbsp of cream cheese frosting. Using the back for the spoon, spread the remaining frosting in any way you prefer.
Serve right away or chill before serving. The colder the cake gets, the firmer the cream will be and vice versa.