Wash and peel the potatoes and then, using a mandolin slicer or a sharp knife, thinly slice the potatoes into rounds. Aim for slices that are about 1/8 inch thick for even cooking.
Let them rest in a bowl full of cold water until you are ready to use them, so they don't go black.
In a saucepan over medium heat melt the butter.
Once melted, add the flour and whisk continuously to create a roux.
Cook for 1-2 minutes until the mixture becomes a light golden colour.
Gradually pour in the heavy cream, whisking constantly to avoid lumps.
Continue to cook and whisk until the mixture thickens, forming a smooth and velvety sauce.
You can now stir in the grated Parmesan cheese until it's fully melted into the sauce.
Season with salt and pepper to taste. If you're adding diced ham, fold it into the sauce at this point for an extra savoury kick.
Time to build and layer your dish. In your air fryer basket or a tray that fits in it, create a layer of thinly sliced potatoes.
Pour a portion of the cheese sauce over the potatoes, ensuring an even coating. Repeat the process, layering potatoes and sauce until you've used up all the ingredients.
Finish it with a sprinkle of some extra Parmesan cheese on top for a golden, crispy finish during air frying.
Preheat your air fryer to 190°C. Once preheated, carefully place the tray or basket in the air fryer.
Cook for 20-25 minutes or until the potatoes are tender, and the top layer is golden brown and crispy. Check for doneness by inserting a fork into the potatoes; they should be soft and easily pierced.
Once cooked, carefully remove the air fryer basket or tray. Sprinkle the finely chopped chives over the top for a burst of freshness and colour.
Allow the scalloped potatoes to cool for a few minutes before serving.