Prep the air fryer: Preheat your air fryer to 320°F (160°C) for 3–5 minutes. This helps the cookies bake evenly. Line the basket with parchment or a silicone liner with holes. Do not preheat with loose parchment.
Cream the butter and sugars: In a medium bowl, beat the softened butter, granulated sugar, and brown sugar together until creamy and slightly fluffy, about 1–2 minutes.
Add egg yolk and vanilla: Stir in the egg yolk and vanilla until smooth and glossy. Scrape the bowl so everything’s well combined.
Mix dry ingredients: In a small bowl, whisk the flour, baking soda, and salt. Add to the wet ingredients and mix just until a soft dough forms. Avoid overmixing.
Fold in chocolate chips: Stir in the chocolate chips until evenly distributed. If the dough feels sticky or warm, chill for 10 minutes to help the cookies hold shape.
Portion the dough: Scoop 1 heaping tablespoon of dough per cookie. Roll into balls and place in the lined basket, leaving at least 1–1.5 inches between them. Work in batches if needed.
Flatten slightly: Gently press each dough ball to about 1/2 inch thick. This helps them spread just right in the air fryer.
Bake: Air fry at 320°F (160°C) for 6–8 minutes, until edges are lightly golden and centers look just set. Cookies will firm up as they cool.
Rest and finish: Let cookies cool in the basket for 3–5 minutes, then move to a rack. Sprinkle with flaky sea salt if you like that salty-sweet finish.
Repeat with remaining dough: Bake the rest in the next batch. Every air fryer is different; adjust time by 1–2 minutes as needed.