I think this works best if you combine all the dry ingredients while you're melting the butter. Add the egg into the dry ingredients and mix. Add the vanilla directly to the butter. Then transfer main chocolate mixture into butter/vanilla mixture and stir til combined. Microwave 75 seconds. This makes one large cake, ideal for 2 people/servings but I'm only going to count it as one in the nutrition facts. This was the original recipe if you're interested, i modified it to suit my taste. https://www.ruled.me/keto-chocolate-cake-mug/

1 Large Egg 2 Tbsp. Salted Butter 2 Tbsp. Almond Flour 1 5/6 Tbsp. Unsweetened Cocoa Powder 1 3/4 Tbsp. Erythritol or Splenda 2 tsp. Coconut Flour 1 tsp. Vanilla Extract 1/2 tsp. Baking Powder

Melt the butter in the microwave for 25 seconds.
Add the rest of the ingredients and mix well.
If you are making 2 servings, split the batter into 2 ramekins.
Microwave for 60-75 seconds.
Whip some heavy cream and put on top. (Optional)