In a large bowl, whisk together flour, baking soda, salt, and sugars until well blended. Stir in chocolate chips. Store in an airtight container.
To make the cookie dough:
Adjust oven rack to center position. Preheat oven to 325°F. Line cookie sheets with parchment paper (or spray with nonstick cooking spray).
Fluff/stir cookie mix to aerate and redistribute the chocolate chips. Measure 4 scant cups of Chocolate Chip Cookie Mix into a bowl, using a knife to level each cup. By hand or with an electric mixer, blend in cooled melted butter, whole egg, egg yolk, and vanilla. Mix until combined.
Use a tablespoon or small cookie scoop to measure out cookie dough and roll it into a ball. Place ball on prepared cookie sheet and flatten slightly. Repeat, spacing cookies two inches apart.
Bake for 9 to 11 minutes or until edges of cookies are starting to turn golden brown and centers are puffy yet set. Remove from oven and allow cookies to cool completely on cookie sheets.
To make LARGE cookies, use a scant ¼ cup of dough. Roll it into a ball and slightly flatten out on the cookie sheet. Space cookies 2 ½ inches apart and bake for 15 to 18 minutes.