Chocolate Chip Cookie in a Cup

Name: Chocolate Chip Cookie in a Cup
Prep time: 5 min
Cook time: 1 min
Total time: 6 min
Cuisine: American
Ingredients: 1 Tablespoon Butter; 1 Tablespoon Granulated White Sugar; 1 Tablespoon of firmly packed Dark Brown Sugar; 3 Drops of Vanilla Extract; Small Pinch of Kosher Salt; 1 Egg Yolk (discard the egg white or save for different recipe); Scant 1/4 of All Purpose Flour (slightly less than 1/4 of a cup); 2 heaping tablespoons of Semi Sweet Chocolate Chips plus more for topping