Preheat the oven to 200°C/fan180°C/gas 6. Gently heat the oil in a deep frying pan, add the onion and pancetta and fry for 3-4 minutes until golden. Add the mushrooms, turn up the heat and fry for 3-4 minutes. Add the garlic and fry for another minute.
Add the chicken, gravy and crème fraîche and bring to a boil. Simmer for 5 minutes until thickened slightly. Stir in the spinach and allow to wilt for 30 seconds. Use to fill 8 pancakes, roll up and lay in an ovenproof dish, top with the cheese and bake for 15-20 minutes until golden. Serve with a salad.
