Add the butter to a saucepan over medium heat.

Melt Phase (1–2 minutes): Butter melts completely and turns pale yellow.

Foam + Bubble Phase (2–4 minutes): Butter foams and bubbles loudly as the water cooks out.

Browning Phase (1–2 minutes): The bubbling slows down, brown specks form on the bottom, and the butter turns golden with a nutty aroma. Stir often.

As soon as the butter reaches deep golden brown, remove from heat immediately to avoid burning.

Transfer to a heat-safe bowl and cool 10–15 minutes until warm, not hot.

Whisk the brown sugar and granulated sugar into the cooled brown butter.

Add the egg, egg yolk, and vanilla, whisking until smooth and glossy.

In another bowl, combine the flour, baking soda, baking powder, salt, nutmeg, and cinnamon.

Stir the dry mixture into the wet until a soft dough forms.

Cover and chill the dough for 30–60 minutes.

Browning the butter warms the dough, so this step helps prevent overspreading and gives you thick, chewy cookies.

Preheat the oven to 350°F.

Scoop 1–2 tablespoon portions and roll into smooth balls. Keep them round — do not flatten.

Optional: roll in sugar mixed with a pinch of nutmeg.

Bake 9–11 minutes, until edges are set but centers still look slightly underbaked.

Cool on the pan for 10 minutes before transferring to a cooling rack.