Melt the butter in a microwave-safe bowl for 30-45 seconds, ensuring it remains slightly warm but not bubbling, then set aside to cool.

In a large mixing bowl, combine flour, baking soda, cornstarch, and kosher sea salt. Whisk until evenly blended, about 1 minute.

In a stand mixer, beat the melted butter with granulated sugar and brown sugar for 1 minute until creamy. Add orange zest and vanilla, beat for an additional minute.

Slowly add eggs one at a time, mixing well after each addition. Gradually incorporate the dry ingredients on low speed until a soft dough forms.

Gently fold in the chopped dark chocolate. Cover the bowl with plastic wrap and chill the dough in the refrigerator for at least 2 hours.

Preheat your oven to 350°F (175°C) and line two baking sheets with parchment paper.

Scoop out about 1.5 tablespoons of cookie dough for each cookie and place them on the prepared baking sheets with 2 inches of space between them.

Sprinkle the tops of each dough scoop with sea salt and bake for 11-13 minutes, rotating the sheets halfway through.

Let the cookies cool on the pan for 5 minutes before transferring them to a wire rack. Allow to cool completely before serving.