Prep your air fryer and dishes. Preheat the air fryer to 350°F (175°C) if your model requires it. Lightly grease two 8-ounce ramekins or one small (6–7 inch) oven-safe dish that fits in your basket.

Peel and slice the apples. Peel if you like a softer texture, or leave the skins on for extra fiber. Core and slice into thin, even pieces, about 1/4 inch thick. Aim for around 3 cups sliced apples.

Toss the apple filling. In a bowl, mix apples with 1 tablespoon brown sugar, 1 tablespoon granulated sugar, 1/2 teaspoon cinnamon, a small pinch of nutmeg, 1 teaspoon lemon juice, 1/2 teaspoon vanilla, and 1 teaspoon cornstarch. Stir until the apples are evenly coated and glossy.

Make the crisp topping. In another bowl, combine 1/3 cup old-fashioned oats, 1/4 cup all-purpose flour, 2–3 tablespoons brown sugar, and a pinch of salt. Cut in 3 tablespoons cold, diced butter with your fingers or a fork until you get coarse, pea-sized crumbs. Stir in 2 tablespoons chopped nuts if you like.

Assemble. Divide the apples between the ramekins, pressing down lightly to pack them in. Sprinkle the topping evenly over the apples, leaving some craggy bits for extra crunch.

Air fry. Place ramekins in the air fryer basket. Cook at 350°F (175°C) for 14–18 minutes, until the topping is deep golden brown and the apples are bubbling around the edges. If the top browns too fast, tent with a small piece of foil for the last few minutes.

Rest and serve. Let the crisps rest for 5–10 minutes. This helps the juices thicken. Serve warm with a scoop of ice cream or a dollop of whipped cream.