Preheat oven to 350F or 180C.

In a bowl, whisk together melted butter and sugars until incorporated.

Add eggs, egg yolk, vanilla extract into the mixture and whisk for a few seconds until well combined. Add baking soda and salt. Mix well unil thoroughly incorporated.

Gradually add flour into the mixture until there are no lumps and a batter is formed.

Fold dark chocolate into the batter and mix evenly.

With an ice cream scooper, scoop a portion and place it on a cookie pan or a pan lined with parchment paper. Make sure to keep it about 2 inches apart.

Bake for 15-20 minutes or until crisp brown.