Tried & tested:
Soak 15 gram dried porcini in hot water for 20 minutes.
Heat oil, add one clove of garlic, crush gently and cook for 2 minutes. Discard garlic.
Add 75 gram diced pancetta or bacon and fry for 4 minutes.
Add drained dried porcini (chopped finely) and 225 gran chopped button mushrooms. Fry for 2 minutes and add soaking liquid from the mushrooms (about 6 table spoons). Simmer for 10 minutes.
Cook pasta, adding remaining soaking liquid from the mushrooms.
Add a can of tuna to the sauce and taste for pepper and salt.
Toss pasta with the sauce and serve with grated Parmesan.
Note: leave out pancetta (or even the tuna) for a vegetarian version. Update: tried it and it doesn't taste as good. You need some pancetta, if only a little.