Add the butter to a light-colored saucepan. Cook over medium heat, stirring often, as it melts and then foams. Continue cooking and stirring until the milk solids on the bottom turn deep golden brown and the butter smells nutty, 5–8 minutes. Remove from heat immediately.
1 cup unsalted butter
Pour the browned butter into a heat-safe bowl, scraping in all the browned bits. Let cool at room temperature for about 25–30 minutes, until no longer hot and just slightly warm to the touch.
1 cup unsalted butter
In a medium bowl, whisk together the flour, baking soda, baking powder, and salt until well combined. Set aside.
2 1/2 cups all-purpose flour, 1 teaspoon baking soda, 1/2 teaspoon baking powder, 3/4 teaspoon fine sea salt
Once the butter has cooled, add the granulated sugar and light brown sugar to the bowl. Whisk for 1–2 minutes until the mixture looks glossy and slightly thickened.
1 cup unsalted butter, 1 1/4 cups granulated sugar, 1/4 cup light brown sugar
Whisk in the egg, egg yolk, and vanilla extract until the batter is smooth, thick, and slightly lighter in color. If the mixture looks separated at first, keep whisking until it comes together.
1 large egg, 1 large egg yolk, 2 teaspoons pure vanilla extract
Add the dry ingredients to the wet ingredients in two additions, folding gently with a spatula or wooden spoon just until no dry streaks remain. The dough will be thick and slightly shiny.
2 1/2 cups all-purpose flour, 1 teaspoon baking soda, 1/2 teaspoon baking powder, 3/4 teaspoon fine sea salt
Cover the bowl tightly and refrigerate the dough for at least 45–60 minutes, or up to 24 hours. If chilling overnight, let the dough sit at room temperature for 10–15 minutes before scooping.
When ready to bake, preheat the oven to 350°F (175°C). Line two baking sheets with parchment paper or silicone baking mats.
In a small bowl, combine the rolling sugars (granulated and coarse, if using). Use a 1.5–2 tablespoon cookie scoop or spoon to portion the dough into balls. Roll each ball until smooth, then coat lightly in the sugar mixture. Place on prepared baking sheets, spacing about 2–3 inches apart.
1/4 cup granulated sugar, 2 tablespoons coarse or sanding sugar
Bake for 9–12 minutes, until the cookies are puffed, the edges look set, and the centers are still slightly soft and pale. The tops may crack slightly. Do not overbake.
Let the cookies cool on the baking sheet for 5–10 minutes, then transfer to a wire rack to cool completely. Serve warm or at room temperature.