**Brown the Butter:**

1. – Add the butter to a pot and heat over medium heat until it melts and simmers.
2. – Continue to simmer until the butter gives off a nutty scent and browns (about 5 minutes).
3. – Measure out 6 tablespoons of browned butter into a small bowl and refrigerate until it reaches the consistency of softened butter.

**Prepare the Dough:**

1. – Preheat the oven to 350°F.
2. – In a medium bowl, whisk together the flour, baking powder, baking soda, and salt.
3. – In a large bowl, cream the cooled brown butter, brown sugar, and granulated sugar together with an electric mixer on high speed until light and fluffy (2-3 minutes).

**Add Wet Ingredients:**

1. – Mix in the egg yolk and vanilla on medium-high speed until pale and fluffy (1-2 minutes).

**Combine Ingredients:**

1. – Add the dry ingredients to the wet ingredients and mix on low speed until just combined.
2. – Fold in the chocolate chips using a rubber spatula.

**Shape and Bake:**

1. – Form the dough into a large ball and slightly flatten it into a disk about 1 ½ inches thick.
2. – Place the dough in the center of a parchment-lined cookie sheet.
3. – Sprinkle extra chocolate chips on top and bake for 21-24 minutes, until golden brown.

**Finishing Touches:**

1. – After baking, sprinkle a few more chocolate chips and some flaky sea salt on top.
2. – Let the cookie cool on the baking sheet for 15 minutes before transferring to a cooling rack, or enjoy it straight from the sheet!