Instructions

1. Heat the butter in a pan and gently sauté the onion until softened, then add the garlic and thyme, and cook for 5 minutes.
2. Meanwhile finely chop the mushrooms and half of the chestnuts. Add these to the onion and season with salt & pepper. Cook for a further 5 minutes.
3. When the liquid in the pan has evaporated, turn off the heat, then let it cool.
4. Transfer half of the cooked mixture into a blender, the other half in a large mixing bowl.
5. Add the rest of the chestnuts to the blender and whiz until you get a paste.
6. Transfer the paste to the bowl, combine it with the rough mixture. Grate the mozzarella over it and mix well.
7. Form six bowls of the mixture and flatten these slightly between your palms. Rest them in the fridge until cooking.
8. Griddle, fry or grill the patties for 8 minutes, then turn over and cook for a further 5 minutes.
9. Serve warm.