1) Cut the veal into 2.5cm cubes, discarding any fat or gristle. 2) Season the flour with salt and pepper and toss the veal in the flour. 3) Heat the butter and oil in a saucepan and, when hot, fry the veal on all sides until golden brown. 4) Gradually stir in the boiling water and bring back to the boil, stirring continuously. 5) Simmer for 2 minutes until the sauce thickens. 6) Stir in the wine and tomato paste. 7) Continue to simmer while you peel the onions. Leave them whole and add them to the pan. 8) Simmer the mixture, uncovered so that the sauce reduces during cooking, for 1½-2 hours. 9) 30 minutes before serving, rinse and slice the mushrooms. 10) Pour boiling water over the tomatoes and peel them. Chop into small pieces and stir into the stew with the mushrooms. 11) Check the seasoning just before serving, and sprinkle with the parsley.