Step 1: Brown the butter. In a light-colored saucepan, melt the unsalted butter over medium heat. Continue cooking, stirring occasionally, until the butter turns a nutty brown color and fragrant, about 5-7 minutes. Immediately transfer to a large heatproof bowl and let cool for 10-15 minutes.
Step 2: Cream wet ingredients. To the cooled browned butter, add the light brown sugar and granulated sugar. Whisk vigorously for 2-3 minutes until light and fluffy. Beat in the eggs one at a time, ensuring each is fully incorporated before adding the next. Stir in the vanilla extract.
Step 3: Combine dry ingredients. In a separate medium bowl, whisk together the all-purpose flour, baking soda, and sea salt.
Step 4: Mix wet and dry. Gradually add the dry ingredients to the wet ingredients, mixing on low speed or by hand with a spatula until just combined. Be careful not to overmix the dough.
Step 5: Fold in chocolate. Gently fold in the semi-sweet chocolate chips, milk chocolate chunks, and chopped dark chocolate until evenly distributed.
Step 6: Chill the dough. Cover the bowl with plastic wrap and refrigerate the cookie dough for at least 24 hours, or up to 72 hours, for the best flavor and texture.
Step 7: Preheat and scoop. When ready to bake, preheat your oven to 375°F (190°C). Line two baking sheets with parchment paper or silicone mats. Scoop rounded tablespoons of chilled dough onto the prepared sheets, leaving about 2 inches between cookies.
Step 8: Bake cookies. Bake for 10-12 minutes, rotating the baking sheets halfway through, until the edges are golden brown and set, but the centers still look slightly soft. For a chewier cookie, avoid overbaking.
Step 9: Cool and serve. Remove from the oven and let cool on the baking sheets for 5 minutes before transferring to a wire rack to cool completely. Enjoy warm or at room temperature.