Brown the butter: In a light-colored saucepan over medium heat, melt the butter, swirling occasionally. Cook until it turns amber, brown specks form at the bottom, and it smells intensely nutty. Immediately remove from heat and pour into a large bowl to cool for 10-15 minutes.
Mix wet ingredients: To the cooled brown butter, add brown sugar and granulated sugar. Beat for 2-3 minutes until smooth and combined. Add the egg and vanilla extract, and beat again until the mixture is creamy and glossy.
Combine dry ingredients: In a separate bowl, whisk together the flour, baking soda, and fine sea salt until evenly distributed.
Combine mixtures: With the mixer on low, gradually add the dry ingredients to the wet ingredients. Mix just until combined and no flour streaks remain. Do not overmix.
Add the chocolate: Using a rubber spatula, gently fold in the roughly chopped chocolate, including the small shards and dust, until evenly distributed throughout the dough.
Scoop and freeze: Scoop 3-tablespoon sized dough balls onto a parchment-lined tray. Cover tightly with plastic wrap and freeze for 24 hours. Do not skip this step.
Bake from frozen: Preheat oven to 190°C (375°F). Place frozen dough balls on parchment-lined baking sheets, leaving at least 3 inches of space between them. Bake for 11-13 minutes, until edges are golden brown and set but centers still look soft. Cool on baking sheet for 5-10 minutes, then transfer to a wire rack.
