In a medium bowl mix flour, brown sugar, sugar, baking powder, and salt. Mix well.
In another bowl, beat together milk, butter, eggs, and vanilla until well combined. Add dry ingredients and beat until just combined – do not over-mix.
Fold in chocolate chips.
Spoon into a muffin tin filled with cupcake liners. Fill them to about ⅔ full. Sprinkle tops with sugar and bake for 16-18 minutes.
Test for doneness by inserting a toothpick into the center. When it comes out clean or with a few crumbs they are done. Allow the muffins to cool a bit in the pan before placing them on a wire rack to cool completely.