First, melt the butter directly in your mug or ramekin by microwaving for about 30 seconds.
Next, stir in the vanilla extract until it's well combined with the melted butter.
Add the sweetener, protein powder, cocoa powder, almond flour, and baking powder, then crack in the egg. Mix all ingredients thoroughly until you have a smooth batter, then gently level the top.
Microwave your mug cake for 60-75 seconds. It's ready when a toothpick inserted into the center comes out clean, ensuring your cake remains wonderfully moist. If you prefer to bake, place it in an oven-safe ramekin and bake at 350°F (175°C) for 10-15 minutes.
Optionally, sprinkle with sugar-free chocolate chips and add a dollop of sugar-free whipped cream. For delightfully melty chocolate chips, microwave the cake for an extra 5-10 seconds before adding the cream.