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

In a large bowl, whisk together the melted butter, brown sugar, and granulated sugar. Add the egg and egg yolk and whisk until well combined and no streaks of egg white remain. Whisk in the vanilla.

Add the dry ingredients to the wet ingredients and mix with a spatula. When the dry and wet ingredients are mostly combined, add the chocolate chips and mix until a soft cookie dough forms and no dry flour remains.

Cover and refrigerate for at least 30 minutes and up to 2 days. Cookie dough chilled for just 30 minutes will yield flatter cookies that spread more as they bake. Cookie dough chilled for 2 hours or more will yield thicker cookies that spread less.

Preheat the oven to 350°F and line two large baking sheets with parchment paper.

Use a 2-tablespoon cookie scoop to scoop the dough onto the baking sheets, leaving at least 2 inches between cookies. Bake, one sheet at a time, for 9 to 11 minutes, or until the edges of the cookies are golden brown but the tops are still pale. They will look underdone when you take them out of the oven, but they will set up as they cool.

Let cool on the baking sheets for 10 minutes before transferring to a wire rack to cool completely.