Step 1

In a medium bowl, whisk together the flour, baking soda and salt.

Step 2

In a separate large bowl, cream together the melted butter and sugars until fluffy. Beat in the vanilla, egg and egg yolk until light and creamy. Mix in the dry ingredients until just combined.Fold in the chocolate chips.

Step 3

Refrigerate cookie dough, covered, for 2 to 3 hours. When ready to bake, Preheat the oven to 325 degrees F.

Step 4

Line two baking sheets with parchment paper and set aside. Scoop 1-2 tablespoon-sized balls onto prepared cookie sheets, about 2 inches apart.

Step 5

Bake for 12 to 15 minutes, or until the edges are lightly browned but the centers still look slightly underdone. Remove from oven and allow to cool on baking sheets completely.