Brown the butter. Add the butter to a light-colored saucepan over medium heat. Melt, then cook, stirring, until it foams and the milk solids turn deep golden and smell nutty, 5–8 minutes. Remove from heat as soon as the specks are amber, not black.

Cool the butter. Pour the brown butter and browned bits into a heatproof bowl. Let it cool 15–20 minutes until just warm, not hot. If you add hot butter to sugar, your dough can turn greasy.

Mix the sugars and butter. In a large bowl, whisk the brown sugar and granulated sugar with the cooled brown butter until glossy and combined, 1–2 minutes.

Add eggs and vanilla. Whisk in the eggs one at a time until the mixture thickens and looks smooth and ribbony. Stir in the vanilla.

Combine dry ingredients. In a separate bowl, whisk the flour, baking soda, baking powder, and salt. This prevents clumps and ensures even rise.

Bring the dough together. Switch to a spatula and fold the dry ingredients into the wet just until no dry streaks remain. Do not overmix.

Add the mix-ins. Fold in the chocolate chips, toffee bits, and pecans if using. Reserve a small handful of chocolate and toffee for pressing on top later.

Chill the dough. Cover and refrigerate for at least 30–60 minutes. Chilling helps prevent spreading and deepens flavor. For thick cookies, chill 2 hours or overnight.

Preheat and prep. Heat your oven to 350°F (175°C). Line baking sheets with parchment paper.

Scoop. Use a 2-tablespoon scoop for standard cookies or 3 tablespoons for bakery-style. Space them about 3 inches apart.

Bake. Bake 9–11 minutes for smaller cookies or 11–13 minutes for larger ones, until edges are set and centers look slightly underbaked. They’ll finish setting as they cool.

Finish. While hot, press a few reserved chocolate chips and toffee bits onto the tops. Sprinkle lightly with flaky salt. Let cool on the sheet 5 minutes, then move to a rack.