Thaw 450 g frozen spinach and press out all the liquid well. Finely chop 1 onion and 2 cloves of garlic.

Heat 1 tbsp olive oil in a pan and gently sauté the onion and garlic for 2-3 minutes. Add the spinach and fry for 2 minutes. Season with 0.5 tsp salt and 0.25 tsp pepper. Remove from the heat.

Melt 40 g butter in a saucepan over medium heat. Whisk in 40 g plain flour and let it cook for 1 minute.

Add 5 dl milk a little at a time, whisking constantly. Cook the sauce through for 3-4 minutes until it thickens.

Season with 0.5 tsp grated nutmeg, 0.5 tsp salt and 0.25 tsp pepper.

Grease an ovenproof dish that fits in your air fryer. Spread a thin layer of béchamel sauce over the bottom.

Place 3 lasagne sheets on top. Spread over half the spinach and a third of the béchamel sauce. Sprinkle with a little mozzarella.

Repeat with 3 lasagne sheets, the rest of the spinach and another third of the sauce.

Finish with the last 3 lasagne sheets, the remaining béchamel sauce and sprinkle with 150 g mozzarella and 50 g parmesan.

Preheat the air fryer to 180 °C.

Place the dish in the air fryer and cover loosely with a piece of air fryer paper or foil for the first 15 minutes so the cheese doesn't get too dark.

Bake for 20 minutes. Then remove the paper and bake for a further 5-8 minutes, until the cheese is golden and bubbling. (Check a couple of times along the way.)

Let the lasagne rest for 5-10 minutes before serving so it can set.