Preheat the oven to 350°F (175°C) and line two baking sheets with parchment paper.
In a large bowl, whisk the melted butter with the brown and granulated sugars until smooth.
Whisk in the egg, egg yolk, and vanilla until combined.
Add the flour, baking soda, and salt, and stir until just combined. Fold in the chocolate chips.
Scoop 2-tablespoon mounds of dough onto the baking sheets, spacing them about 2 inches apart.
Bake for 10-12 minutes, until the edges are golden but the centers still look slightly underdone. Cool on the pan for 5 minutes before transferring.