Prep the air fryer. Preheat your air fryer to 325°F (165°C) for 5 minutes.
Line the basket or tray with a perforated parchment sheet or a light coat of nonstick spray. If using parchment, trim it so it doesn’t block airflow.
Melt butter and chocolate. In a heatproof bowl, microwave 1/2 cup (1 stick) butter with 1 cup semi-sweet chocolate in 20–30 second bursts, stirring between each, until smooth. Let it cool for 3–4 minutes so it’s warm, not hot.
Whisk in sugars. Add 1/2 cup granulated sugar and 1/2 cup packed brown sugar to the warm chocolate mixture.
Whisk until glossy and slightly thick, about 30 seconds.
Add eggs and vanilla. Whisk in 2 large eggs, one at a time, followed by 1 teaspoon vanilla. Beat for 45–60 seconds until the batter looks shiny and pulls into ribbons. This helps create that crackly top.
Combine dry ingredients. In a small bowl, whisk 3/4 cup all-purpose flour, 2 tablespoons cocoa powder, 1/2 teaspoon baking powder, and 1/4 teaspoon fine sea salt.
Fold to finish the dough. Use a spatula to fold the dry mix into the wet until just combined.
If using mix-ins, fold in up to 1/2 cup chocolate chips or nuts now. The dough will be thick and glossy.
Chill briefly. Refrigerate the bowl for 10–15 minutes. Don’t skip this—a short chill helps prevent overspreading in the air fryer.
Scoop. Use a 1.5-tablespoon scoop to portion mounds onto the lined air fryer tray, leaving about 1.5 inches between each. Work in batches so cookies have space and air can circulate.
Air fry. Cook at 325°F (165°C) for 6–8 minutes.
The tops should be shiny with small cracks, and the edges set. The centers will look soft—that’s perfect for fudgy cookies.
Cool. Let cookies sit in the basket for 3 minutes to firm, then transfer to a rack. They’ll continue to set as they cool.
Repeat. Continue with remaining dough, adjusting time by 1 minute if your air fryer runs hot or cool.
If dough softens too much, pop it back into the fridge between batches.
Finish with flair. While warm, top with a pinch of flaky sea salt for contrast, if you like.