In a microwaveable mug, melt butter and chocolate together. Stir until chocolate is completely melted and mixture is smooth. Let mixture cool to room temperature.
Using a fork, whisk in egg. Sprinkle in almond flour, baking powder, and Splenda Stevia Sweetener Packets. Stir together. Add in chocolate chips if using.
Pour mixture into a dome-shaped mug sprayed with nonstick spray. Microwave on high for 50 seconds. (Each microwave is different, so check the cake and add 10 seconds if needed.)
Remove and let cake cool for 30 seconds. Enjoy cake straight out of the mug, or carefully turn it out onto a plate.
