Fry the onion in a splash of olive oil, season the chicken pieces with salt and pepper and brown them gently in the oil, add the garlic and fresh mushrooms, add the wine (stock) and turn the heat down, simmer gently until the chicken is cooked through and the wine (stock) has reduced a little.
Meanwhile, cook the spaghetti in plenty of boiling, salted water and then drain well.
Add the cream to the pan of chicken then bring to the boil and turn the heat off, season well with salt and pepper.
Add the drained spaghetti to the creamy chicken sauce and toss well, add the Parmesan cheese (or cheddar) and all of the basil and stir well.
Transfer to an ovenproof dish, sprinkle with cheddar cheese and bake in the oven until golden brown, bubbling and crisp.
Divide between your plates, drizzle with olive oil and sprinkle the rest of the cheese over before serving. Serve with a salad.