Brown the butter by melting the unsalted butter in a medium saucepan over medium-low heat, stirring continuously for about 5-7 minutes until golden brown and nutty.

In a mixing bowl, mix the browned butter with light brown sugar and granulated sugar, then whisk in the egg, egg yolk, and vanilla extract until smooth.

In another bowl, whisk together flour, baking soda, and salt. Gradually add this to the wet mixture, mixing gently until just combined.

Fold in the chocolate chips until evenly distributed. Add any additional mix-ins like nuts if desired.

Chill the dough for at least 1 hour, covered with plastic wrap.

Preheat the oven to 350°F (175°C) and line a baking sheet with parchment paper. Let the dough sit at room temperature for 20 minutes.

Scoop the dough into balls and space them 2 inches apart on the baking sheet.

Bake for 12-13 minutes until edges are golden and centers are soft. Sprinkle with sea salt if desired and cool on a wire rack.