Preheat oven to 325 degrees F (165 degrees C).

In an electric mixer fit with paddle attachment, cream together butter with brown and white sugars until thoroughly combined.

Add vanilla extract, egg, and egg yolk. Beat on medium for 2 minutes or until fluffy.

In a separate bowl, combine flour, baking soda, and salt (stir to combine).

Add flour mixture to wet ingredients and stir until combined.

Stir in dark chocolate chunks with wooden spoon.

Drop large spoonfuls of cookie dough onto your baking pan.

Optional: Sprinkle the top of each cookie dough ball with sea salt.

Bake for 15-17 minutes (or until edges are lightly golden). Remove and allow to cool!