This mug sugar cookie is unlike no other. It uses a secret ingredient to keep your cookie soft and chewy even after baking it in the microwave you have to try it!
First, start by melting the butter in the mug in the microwave. This can take anywhere from 15-30 seconds depending on if your butter was at room temperature or not.
Add in the granulated sugar, the brown sugar, and the salt and stir until combined. Add in the egg yolk and the vanilla and stir one last time.
Add in the all purpose flour and the corn starch and mix just until combined. Flatten the top with a mini rubber spatula or the back of a spoon then sprinkle with the 1/2 tsp granulated sugar for a traditional sugar cookie taste.
Bake in the microwave for 40-50 seconds. Check your mug cookie after 40 seconds, if it is not fully bake din the center bake it for another 5-10 seconds. Enjoy as soon as you make it!