Via: Kris Kirkham
Heat a large frying pan, add the chopped walnuts and toast them over a medium heat for 2 mins. Set aside.
Slice the chestnut mushrooms and bring a large pan of salted water to the boil.
Return the frying pan to the heat and melt half the butter. Add the mushrooms and fry over a high heat, stirring occasionally until golden. Set aside.
Add the pasta to the pan of boiling water and cook for 7-8 mins or until al dente.
Meanwhile, return the frying pan to the heat. Add the remaining butter, shallots, garlic and two-thirds of the thyme. Cook gently for 5 mins, then return the mushrooms to the pan. Increase the heat, pour in the wine or stock and season well. Bubble for 2 mins until reduced, then stir in the crème fraîche and half the cheese.
Drain the pasta, reserving 2 tbsp of the cooking water, and return to the pan. Add the mushrooms, sauce and reserved cooking water and toss to coat. Season.
Divide between 2 bowls, then crumble over the remaining cheese and sprinkle with the walnuts and remaining thyme.