In a food processor, crush nutter butter cookies until fine crumbs form.
Add the crumbs, sugar, and baking powder to a 6-8oz. microwave safe mug, and stir.
Add the milk and mix to combine.
Microwave for 1 minute, adding 10 seconds more if needed.
Remove from the microwave and let cool for 2-3 minutes before serving.
Dust with powdered sugar and top with a chopped Reeses’s cup.
Notes
Microwave times may vary based on microwave strengths, so starting at 1 minute and adding 10 additional seconds at a time will help fully cook the mug cake.3 cookies equals 1.6 ounces of crumbs.