Prep the pan: Line a small, air-fryer-safe pan or dish with parchment. A 6–7 inch square pan or mini loaf pan works well. Lightly spray with oil for easy release.

Mix dry ingredients: In a bowl, combine oats, protein powder, cinnamon, salt, and optional chia or flax. Stir to distribute evenly.

Stir wet ingredients: In another bowl, whisk nut butter, honey or maple, milk, vanilla, and egg (if using) until smooth. Warm the nut butter for 10–15 seconds in the microwave if it’s too thick.

Combine: Pour the wet mixture into the dry and fold until a thick dough forms. If it seems crumbly, add 1–2 tablespoons more milk. If it’s too loose, add a tablespoon of oats.

Add mix-ins: Fold in chocolate chips or any extras you like. Don’t overmix—just enough to spread them out.

Press and shape: Transfer the dough to your lined pan. Press into an even layer, about 3/4 to 1 inch thick. Smooth the top with a spatula.

Preheat the air fryer: Set to 320°F (160°C) for 3 minutes to warm up.

Cook: Air fry at 320°F (160°C) for 10–12 minutes. Start checking at 9 minutes. The edges should look set and lightly golden, and the center should spring back when pressed.

Cool completely: Remove the pan and let cool in the pan for 10 minutes, then lift out by the parchment. Cool fully before slicing. This is key for clean cuts and the right texture.

Slice and serve: Cut into 6–8 bars. Enjoy right away or store for later.