Direction :

1. Position an oven rack in the center of the oven. Preheat the oven to 350ºF. Line a rimmed sheet pan with parchment paper.
2. In a small skillet or saucepan with a light-colored interior, melt 8 tablespoons (113 g) of the butter over medium heat. Once melted, cook the butter, stirring constantly, until the milk solids are deep golden brown, about 3 minutes.
3. In a large bowl, combine the brown butter, the remaining 2 tablespoons (29 g) cold butter, and the brown sugar. Whisk until combined and the butter melts, about 1 minutes. The mixture will be a bit grainy and separated.
4. Add the egg, vanilla, and salt and whisk until smooth, thick, and glossy, about 30 seconds.
5. Whisk in the baking powder and soda. Fold in the flour with a spatula and when a few streaks of flour remain, add the nuts and chocolate. Mix until no streaks of flour remain and the chocolate and nuts are evenly distributed in the dough.
6. Use a 1.5-tablespoon cookie scoop or heaping tablespoon to portion the dough into 22 cookies. Alternatively, portion the dough into 35-gram balls. At this point you can refrigerate the cookie dough balls until you are ready to bake or you can proceed: I find I can bake 8 cookies at a time on my half sheet pan. I like to flatten my portioned dough balls slightly after I transfer them to the sheet pan. Sprinkle lightly with flaky sea salt, if using.
7. Bake the cookies until just set with a few cracks on top, 9 to 11 minutes. Let the cookies cool completely on the baking sheet. Repeat with remaining cookie dough balls. Store in an airtight container at room temperature for up to 4 days.