Step 1: Brown the butter by melting it in a saucepan over medium heat until it turns amber and smells nutty. Pour into a bowl and let cool for 10 minutes.
Step 2: In a large bowl, whisk the cooled browned butter with brown sugar and granulated sugar until well combined.
Step 3: Add the egg, egg yolk, and vanilla extract. Beat vigorously for 2 minutes until the mixture lightens in color.
Step 4: Sift in the flour, baking soda, and sea salt. Fold gently with a spatula until just a few streaks of flour remain.
Step 5: Fold in the chocolate chips and chunks. Do not over-mix.
Step 6: Chill the dough in the refrigerator for at least 30 minutes to enhance flavor and prevent excessive spreading.
Step 7: Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.
Step 8: Scoop rounded tablespoons of dough onto the sheet, spacing them 2 inches apart.
Step 9: Bake for 9-11 minutes or until the edges are golden but the centers are still soft.
Step 10: Remove from oven, sprinkle with flaky sea salt, and let cool on the pan for 5 minutes before transferring to a wire rack.