Brown the Butter: Begin by cubing 1 cup of unsalted butter and placing it in a light-colored skillet over medium heat. Stir continuously for about 5-8 minutes until golden brown and nutty aroma develops.

Mix Wet Ingredients: In a large mixing bowl, combine the cooled brown butter with 3/4 cup dark brown sugar and 1/2 cup granulated sugar. Whisk until smooth and creamy. Crack in 1 large egg and whisk vigorously.

Combine Dry Ingredients: In a separate bowl, whisk together 2 cups all-purpose flour, 1 teaspoon baking soda, and 1/2 teaspoon fine sea salt. Gradually fold this into the wet ingredients until just combined.

Fold in Mix-Ins: Gently fold in 1 cup chopped dark chocolate and 1 cup chopped Oreos into the cookie dough.

Chill the Dough: Cover the bowl with plastic wrap and refrigerate the dough for 30-60 minutes.

Bake Cookies: Preheat oven to 350°F (180°C). Scoop tablespoons of dough onto a parchment-lined baking sheet, baking for 10-12 minutes until edges are golden.

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