Prepare the pan: Line a small, air-fryer-safe baking pan (about 7–8 inches square or round) with parchment, leaving overhang for easy lifting. Lightly grease the parchment. If your air fryer basket is small, use two mini pans or ramekins and bake in batches.

Melt the base: In a small saucepan over low heat, melt the butter with the brown sugar and golden syrup. Stir until the sugar dissolves and the mixture looks glossy, about 2–3 minutes. Remove from heat and stir in vanilla and salt. Add cinnamon if using.

Mix the oats: In a large bowl, add the rolled oats. Pour the warm butter mixture over the oats and stir until every flake is coated. Let it cool for 3–4 minutes so the chocolate doesn’t melt on contact.

Fold in the chips: Stir in the mini chocolate chips, reserving a tablespoon to sprinkle on top. Mini chips distribute better and don’t sink as much.

Press it in: Tip the mixture into the lined pan. Press firmly and evenly with the back of a spoon or a flat-bottomed cup. Compacting is key for neat, chewy bars. Sprinkle the remaining chips on top and gently press them in.

Air fry: Preheat the air fryer to 320°F (160°C) for 2–3 minutes if your model recommends it. Air fry the flapjacks at 320°F (160°C) for 14–18 minutes, until the edges are a shade darker and the surface looks set. If browning too quickly, tent loosely with foil.

Cool completely: Remove the pan and let it cool in the pan for at least 30–45 minutes. Lift out with the parchment and cool fully before slicing. They firm up as they cool, so be patient.

Slice and serve: Cut into bars or squares. For cleaner cuts, chill for 15 minutes first. Enjoy slightly warm or at room temperature.