Start by gathering all your ingredients and preheating your oven to 350°F (175°C).
In a large mixing bowl, combine the melted butter, light brown sugar, and granulated sugar. Whisk until smooth and creamy. Add the egg, egg yolk, and vanilla extract, whisking until well incorporated.
In a separate bowl, whisk together the all-purpose flour, baking soda, and salt.
Gradually add the dry ingredients to the wet mixture, stirring gently with a spatula until just combined.
Gently fold in the semi-sweet and milk chocolate chips, reserving a handful for topping.
Using a cookie scoop or tablespoon, drop rounded balls of dough onto the prepared baking sheet, spacing them about 2 inches apart. Bake for 10-12 minutes, or until edges are lightly golden.
Once baked, remove cookies from the oven and immediately press reserved chocolate chips on top. Allow to cool on the baking sheet for 5 minutes before transferring to a cooling rack.
