- Grease cookie sheets or line with parchment paper. Measure out flour using the scoop-and-level method (should be about 120-125 grams).
- Sift together the flour, baking soda and salt; set aside.
- In a medium bowl, cream together the melted butter, brown sugar and white sugar until well blended. Beat in the vanilla, egg, and egg yolk until light and creamy.
- Mix in the sifted ingredients until just blended. Stir in the chocolate chips by hand using a wooden spoon.
- Drop cookie dough 1/4 cup at a time onto the prepared cookie sheets. Cookies should be about 3 inches apart. Refrigerate the cookies for at least 30 minutes, ideally 3 hours or longer.
- Preheat the oven to 325 F. Bake for 15 to 17 minutes, or until the edges are lightly toasted. Cool on baking sheets for a few minutes before transferring to wire racks to cool completely.