Ingredients
Method
Whisk 1¼ cups (156 g) all-purpose flour and ½ tsp. baking soda in a small bowl to combine; set aside.
Toast ¾ cup macadamia nuts in a dry small skillet over medium-low heat, stirring often, until golden, about 5 minutes. Transfer to a cutting board; let cool. Very coarsely chop (you want to keep the pieces large).
Heat ½ cup (1 stick) unsalted butter in same skillet, swirling and scraping bottom of pan often with a heatproof rubber spatula, until it foams, then browns, about 4 minutes. Scrape into a large heatproof bowl; let cool 1 minute.
Add ½ cup (100 g) dark brown sugar, ¼ cup (50 g) granulated sugar, 2 Tbsp. white miso, and 1 tsp. Diamond Crystal or ½ tsp. Morton kosher salt to brown butter and whisk, breaking up any clumps, until sugars are dissolved. Whisk in 1 large egg, room temperature, and 1 tsp. vanilla extract. Working in 2 or 3 batches, sift reserved dry ingredients into bowl, folding after each addition until no dry spots remain. Add nuts, ½ cup semisweet or bittersweet chocolate chips, and ½ cup white chocolate chips and fold until just combined. Cover and chill dough at least 30 minutes and up to 1 day.
Place racks in upper and lower thirds of oven; preheat oven to 350°. Using a #20 cookie scoop (or about 3 Tbsp.), portion out dough, placing 5–6 cookies each on 2 parchment-lined rimmed baking sheets, spacing about 2" apart, and sprinkle with flaky sea salt.
Bake cookies, rotating baking sheets front to back and top to bottom halfway through, until golden around edges, 14–16 minutes. Remove from oven and, using a spatula, lightly press down on cookies. Let cookies cool on baking sheets 5–10 minutes, then transfer to wire racks and let cool completely.