Set the oven racks in the upper and lower thirds of the oven. Preheat to 325˚F and line 2 baking sheets with parchment or lightly grease.
In a medium bowl, whisk together flour, baking soda, and salt.
In a large bowl, beat together butter, light brown sugar, and granulated sugar until fluffy.
Beat in the egg, egg yolk, and vanilla extract.
Stir in the flour mixture until just combined and dough forms. Fold in the chocolate chips.
Roll a teaspoon size piece of dough into a ball, then break into two equal pieces.
Place on the prepared baking sheets 1 inch apart, with torn edges facing up. Repeat with remaining dough.
Bake in preheated oven for 4 minutes. Turn and rotate the baking sheets, then continue to bake until lightly golden, another 3-4 minutes. Allow to cool on baking sheets to room temperature before storing in an airtight container.