Add the butter, sugars, vanilla and milk to a microwave safe dish like a ramekin or mug. (A flat 4-inch/8oz ramekin will bake more evenly than a mug, just FYI.) Mix really well to help dissolve the sugars.
Add the flour, salt, and chocolate chips. Stir well.
Cook in the microwave for about 40-45 seconds. Time will vary depending on the dish used and power of the microwave. Enjoy warm!