Melt the Butter: Place butter in a microwave-safe bowl and heat for 30-45 seconds on full strength until it's almost completely melted but has a few soft pieces left.

Mix Dry Ingredients: In a large mixing bowl, whisk together flour, baking soda, cornstarch, and salt until well combined.

Cream Butter and Sugars: Beat the melted butter along with granulated sugar and brown sugar on medium speed for about one minute until fluffy. Add in orange zest and vanilla extract, continuing to mix for another minute before incorporating eggs one at a time while mixing between additions.

Combine Wet and Dry Ingredients: Turn mixing speed down to low; gradually add in the dry ingredients until just combined or when a soft dough begins to form.

Chill the Dough: Fold in chopped dark chocolate with a spatula gently until evenly distributed throughout the dough. Cover the bowl with plastic wrap and place it in the refrigerator to chill for at least two hours or overnight if possible.

Preheat Oven & Bake Cookies: Preheat your oven to 350 degrees Fahrenheit while lining baking sheets with parchment paper. Use a standard-size cookie scoop to form cookie dough balls on prepared sheets, ensuring two inches between each ball before sprinkling lightly with sea salt if desired; bake for about 11-13 minutes until golden brown on edges.