Pre-heat the air fryer at 200C for 5 minutes.
Heat a pan and add the spinach. Drizzle some oil (optional) and cook until the spinach has wilted completely.
Next, transfer the spinach into a bowl. Add the feta cheese, salt, black pepper powder, garlic powder, egg yolk, and mixed herb seasoning. Mix well.
Take the chicken breasts. Make slits into the breast to insert the filling.
Fill the chicken breasts with the stuffing.
Transfer the stuffed chicken breasts into the air fryer.
Cook the stuffed chicken breasts at 200C for 15 minutes. You can flip them once in the middle.
Serve hot with potatoes and beans on the side.