Preheat the oven to 350° F. In a stand mixer fitted with a hook attachment, beat together the brown sugar, granulated sugar, butter, and shortening until the mixture is incorporated and light in color. Add in the eggs and vanilla extract and mix until combined. Slowly add in the dry ingredients: flour, baking soda, and salt. Allow to mix on low at first, then gradually increase speed as the mixture begins to come together. Stir in the semi-sweet chocolate chips. Using a tablespoon, form the dough into little spherical drops (about 1 ½ tablespoons). Spread the dropped dough 2 inches apart. On a 9 x 13 cookie sheet, 12 drop doughs fit perfectly. Bake for 8-10 minutes or until the bottoms is a light golden brown color. Let cool completely.