Cook the pasta according to the instructions on the packet. At the same time, put the mushrooms in a colander and let them drain. Cut the spring onion into rings, chop the garlic.
Sauté the garlic, mushrooms and spring onions in heated butter, pour in the white wine and stock, add the mascarpone, bring to the boil and simmer for 3 minutes. Season the mushroom sauce with salt and pepper to taste.
Distribute the pasta on preheated plates, pour the mushroom sauce on top, garnish with a little parsley and serve immediately.