Preheat the air fryer: Set it to 320°F (160°C). A slightly lower temp helps the centers cook through without over-browning the tops.

Cream the butter and sugars: In a medium bowl, beat 1/2 cup softened unsalted butter with 1/3 cup granulated sugar and 1/2 cup packed light brown sugar until light and fluffy, about 2 minutes.

Add egg and vanilla: Mix in 1 large egg and 1 1/2 teaspoons vanilla extract until smooth and creamy.

Combine dry ingredients: In a separate bowl, whisk 1 1/2 cups all-purpose flour, 1/2 teaspoon baking soda, and 1/2 teaspoon fine sea salt.

Bring it together: Add the dry ingredients to the wet ingredients and mix just until no dry streaks remain. Don’t overmix.

Fold in the M&Ms: Stir in 3/4 to 1 cup M&Ms. If you like extra sweetness, add 1/4 cup chocolate chips. Save a few M&Ms to press on top before baking.

Chill briefly (optional but helpful): Chill the dough for 15–20 minutes. This keeps the cookies thick and chewy in the air fryer.

Prep the basket: Cut a piece of parchment to fit the air fryer basket. Poke a few small holes to allow airflow. Do not preheat with parchment inside.

Portion the dough: Scoop 1 1/2-tablespoon balls (about a heaping cookie scoop). Place 4–6 dough balls on the parchment, leaving space to spread. Gently flatten to about 3/4 inch thick and press a few M&Ms on top.

Air fry: Cook at 320°F (160°C) for 6–8 minutes. Cookies are done when edges look set and the tops are slightly puffed with light golden spots. They may seem soft—this is good.

Rest to set: Let cookies cool in the basket for 3–4 minutes before moving them. They’ll firm up as they cool.

Repeat: Refresh with a new parchment sheet and bake remaining dough in batches. If the basket gets too warm, wait a minute or two between batches.