Add all ingredients to a microwave-safe mug and stir until completely combined. Note: make sure your butter has cooled before adding it, or else it will melt the chocolate chips before microwaving.
Microwave on high for 30 to 50 seconds (depending on desired texture). For a gooier cookie consistency, microwave just 30 seconds, and for a cake-like consistency, microwave for 50 seconds to one minute.