Mushrooms are cleaned, washed and finely chopped. Stew in the butter until soft (about 10 minutes). Add salt, add tomato paste and 3-4 tbsp hot water. The sauce boil 5 minutes, remove from heat and sprinkle with 1 pinch of pepper. The pasta is cooked, drained, rinsed with cold water and immediately showered with hot sauce. In serving to scatter with grated cheese.