Peel and slice the onion, clean the mushrooms and slice them into thin segments, blanch the tomatoes for half a minute, once peeled, deseeded and drained, chop them into bits. Rinse the parsley in cold water, dry it and chop it.Heat the oil in a pan and fry the onion. Add the porcini and season with salt and pepper. After they have cooked for 5 minutes, add the tomatoes and simmer for 10 minutes, then 5 minutes before removing it from the heat add the parsley to the sauce.Cook the pasta in plenty of boiling salted water, toss it in a serving dish mix it with the sauce, sprinkling the chopped parsley to taste. In case fresh porcini are not available, the chef recommends to use 70% dried porcini, soaking them in cool water for 30 minutes.