Stir vinegar and flour until smooth and mix with about 3 litres of water. Brush black salsifies vigorously under running water, peel and cut off woody ends. Place the black salsifies in vinegar water immediately.
Cut the black salsifies into pieces and cook covered in boiling salted water for about 20 minutes. Cook the pasta in boiling salted water according to the instructions on the packet. Drain the black salsifies, collecting 500 ml of vegetable water.
Heat the fat in a pot and sauté the flour in it. Add vegetable water while stirring, bring to the boil. Add black salsify, peas, wine and cream and simmer at low heat for 4-5 minutes, stirring occasionally.
Season to taste with salt, pepper, sugar and nutmeg. Wash parsley, dab dry, chop finely and add to the sauce. Fry pancetta in a large pan until crispy, remove. Arrange the pasta and black salsify sauce on plates, crumble the pancetta and pour over it.