**Preheat the Oven**: Set your oven to 400°F.
**Cream the Butter and Sugars**: In a large mixing bowl, cream together the cubed butter, sugar, and brown sugar for about 4 minutes until light and fluffy, scraping down the sides halfway through.
**Add Wet Ingredients**: Mix in the egg, egg yolk, lemon zest, lemon juice, and lemon extract (if using). For even more lemon flavor, add extra lemon zest.
**Combine Dry Ingredients**: Gently fold in the flour, cornstarch, baking soda, and salt just until combined. Then fold in the lemon chips or white chocolate chips.
**Form the Cookies**: Roll the dough into 6-ounce balls. Using a food scale can help ensure even baking. Place the dough balls on a light-colored baking sheet to prevent the bottoms from browning too much.
**Bake**: Bake for 9-11 minutes. After baking, let the cookies set up for at least 10 minutes before serving.