Clean the porcini mushrooms with a knife and then delicately rub them with a damp, wrung-out cotton cloth. Slice them thinly and set them aside. Clean and finely chop the shallot. Sauté it with 4 spoonfuls of olive oil in a heavy-bottomed frying pan. When it becomes translucent add the mushrooms, season with salt and pepper and add the torn up sage leaves. Stir and cook over a moderate heat for 10-15 minutes. Toast the crumbled bread and the coarsely chopped hazelnuts in a small, heavy-bottomed frying pan with 1 spoonful of olive oil. Cook the tagliatelle in plenty of boiling, salted water and strain when “al dente” (set aside a little of the water). Tip the pasta into the pan with the hot mushroom sauce, add the grated pecorino and 1 or 2 spoonfuls of the pasta cooking water and mix everything together. Top with the toasted breadcrumbs and hazelnuts, the chopped parsley and a drizzle of “raw” olive oil; stir carefully and serve immediately, nice and hot, in the pan or a pre-heated serving dish. Buon appetito!