Spray a mug (½ cup mug) with baking spray.

Add flour, sweetener, cocoa powder, baking powder, and salt in the mug.

Whisk to blend. Microwave the butter to melt.

Add the melted butter, nonfat milk, and vanilla to the mug. Whisk well to combine.

Use a spoon to mix ½ tablespoon of mini chocolate chips in the mug.

Sprinkle the rest of the chocolate chips and crushed walnuts on top of the batter.

Transfer the mug into the microwave.

Set the temperature on the microwave to high for 40 seconds.

Remove from the microwave and check to see if the cake is fully cooked. Carefully place your finger on the center top of the cake.

If the cake is not done the batter will still be a little runny.

If not done, return the mug to the microwave for an additional 10 seconds.

If it is done, remove the mug from the microwave. (Do not overbake the cake as it will continue to cook in the mug when removed from the microwave.)

Enjoy!