Brown the butter. Add the butter to a light-colored saucepan over medium heat. Stir as it melts, foams, and then turns golden with brown bits forming at the bottom. When it smells nutty and the milk solids are chestnut brown, remove from heat. Pour into a heatproof bowl, scraping in the browned bits. Let cool 20–30 minutes until just warm, not hot.

Preheat the oven to 350°F (175°C). Line two baking sheets with parchment paper or silicone mats.

Whisk the dry ingredients. In a medium bowl, whisk flour, baking soda, baking powder, and fine sea salt until combined.

Mix the sugars and browned butter. In a large bowl, whisk the slightly cooled brown butter with brown sugar and granulated sugar until glossy and smooth, about 1 minute.

Add eggs and vanilla. Whisk in the eggs one at a time until the mixture is thick and slightly lightened, then stir in the vanilla.

Combine wet and dry. Use a spatula to fold the dry ingredients into the wet just until you see a few streaks of flour. Do not overmix.

Fold in chocolate. Stir in the chocolate chips or chunks until evenly distributed.

Chill briefly. Cover the bowl and chill the dough for 20–30 minutes to firm it up. This helps control spread and improves texture.

Scoop the dough. Use a 2-tablespoon scoop (about golf ball size) and space the dough 2 inches apart on the prepared trays.

Bake. Bake one sheet at a time for 10–12 minutes, until edges are set and golden but centers still look soft. Rotate the pan halfway for even baking.

Finish and cool. Sprinkle with flaky sea salt right out of the oven. Let the cookies rest on the sheet for 5 minutes, then transfer to a rack to cool.

Enjoy. These are best slightly warm when the chocolate is gooey, but they’re great at room temperature too.