Brown the Butter: Melt 1 cup of unsalted butter over medium heat in a light-colored skillet, stirring continuously for about 5 to 8 minutes until golden brown.

Mix Wet Ingredients: Whisk together the cooled brown butter, ½ cup dark brown sugar, and ½ cup granulated sugar until creamy. Add 1 large egg and whisk until incorporated.

Combine Dry Ingredients: In a separate bowl, whisk together 2 cups all-purpose flour, 1 teaspoon baking soda, and ½ teaspoon fine sea salt. Gradually add this to the wet ingredients.

Fold in Mix-Ins: Gently fold in 1 cup dark chocolate chunks and 1 cup chopped Oreos until evenly distributed.

Chill Dough: Cover the bowl with plastic wrap and chill the dough in the refrigerator for 30 to 60 minutes.

Bake Cookies: Preheat oven to 350°F, line a baking sheet with parchment paper, scoop tablespoon-sized balls, and bake for 10 to 12 minutes.

Cool: Let cookies rest on the baking sheet for about 5 minutes before transferring to a wire rack to cool completely.