Combine the butter and chocolate into the bottom of a large coffee mug—microwave on high for 30 seconds. Stir and then microwave for another 30 seconds until melted.
Step 2
Add the other ingredients, including the sweetener, baking powder, almond flour, cocoa powder, and mix well.
Step 3
Next, add the egg and vanilla extract. Stir well.
Step 4
Microwave on high for 50-60 seconds. Do not overcook the cake, or it will be dry and not fudgy.
Step 5
Allow the cake to cool slightly while you prepare the dalgona coffee whip. Combine the instant coffee and boiling water together in a small bowl.
Step 6
Whip to a stiff peak using a small whisk and top the chocolate cake with it. Serve immediately. Grate a little dark chocolate top (optional).