In a microwave-safe mug (or ramekin), add brown sugar, milk, vanilla extract, and oil.
Mix well until everything is well-combined.
Add flour, baking powder, baking soda, and salt to mug mixture.
Mix well until the dough comes together.
Add 1 tablespoon chocolate chips and mix till combined.
Top off the dough with 1 tablespoon chocolate chips.
Microwave for 1 minute.
Chocolate chip mug cookie is ready - Let cool slightly and enjoy warm!