Air fryer spinach feta filo parcels

Name: Air fryer spinach & feta filo parcels
Ingredients: knob of butter; 1 large onion finely chopped; 2 garlic cloves finely chopped; 500g frozen spinach defrosted and chopped; 1 egg beaten; 100g feta finely crumbled; 1 tbsp dill or parsley chopped; 4 filo pastry sheets; olive oil spray; 1 tsp sesame seeds or nigella seeds