Cream the butter and sugars: In a mixing bowl, beat the softened butter, powdered sugar, and granulated sugar until light and fluffy, about 2–3 minutes. Aim for a creamy, pale mixture that looks smooth, not greasy.

Add vanilla: Mix in the vanilla extract until fully combined. Scrape down the bowl so everything blends evenly.

Combine dry ingredients: In a separate bowl, whisk the flour, salt, and cornstarch (if using). The cornstarch softens the crumb and keeps the cookies tender.

Bring the dough together: Add the dry ingredients to the butter mixture. Mix on low just until a soft dough forms. It should hold when pressed but not feel sticky.

Chill the dough: Shape the dough into a flat disk, wrap, and chill for 20–30 minutes. This makes it easier to roll and helps the cookies hold their edges in the air fryer.

Prep the air fryer: Line the air fryer basket with a piece of parchment cut to fit, leaving room for airflow. Lightly mist with cooking spray if your parchment isn’t nonstick. Preheat the air fryer to 300°F (150°C) for 3–5 minutes.

Roll and cut: On a lightly floured surface, roll the dough to about 1/4 inch (6 mm) thick. Cut into rounds, squares, or fingers. Re-roll scraps as needed. For a classic look, prick each cookie with a fork.

Arrange in the basket: Place cookies in a single layer on the parchment, leaving a little space between them. Sprinkle with raw sugar if you like a light crunch on top.

Air fry: Cook at 300°F (150°C) for 8–12 minutes, depending on size and your air fryer model. Look for set centers and lightly golden edges. Shortbread should stay pale overall.

Cool completely: Let cookies rest in the basket for 3–5 minutes to firm up, then transfer to a rack. Shortbread develops its best texture as it cools.

Repeat: Continue with remaining dough, keeping unbaked dough chilled between batches for clean edges and even baking.