Mix the wet ingredients

Whisk together the melted butter, brown sugar, and granulated sugar until smooth and glossy. Add the egg, egg yolk, and vanilla, and mix until thick and fully combined.

Mix the dry ingredients

In a separate bowl, whisk together the gluten-free flour, baking soda, baking powder, cornstarch, and salt.

Combine

Add the dry ingredients to the wet ingredients and mix until just combined. Fold in the chocolate chips.

Let the dough rest (don’t skip this)

Let the dough sit for 10–15 minutes. This allows the gluten-free flour to absorb moisture, which is key for a smooth texture.

Scoop and chill

Scoop into tall, mounded balls (about 2 inches high). Chill for 30–60 minutes to prevent spreading.

Bake

Preheat oven to 375°F. Place cookies 2 inches apart.

Bake for 10–12 minutes, until edges are set and centers look slightly underbaked.

Cool

Let cookies rest on the baking sheet for 10 minutes before transferring.