Brush a flameproof casserole with oil, add the pancetta and cook over a low heat until the fat runs. Add the onion and cook, stirring occasionally, for 5-6 minutes until lightly browned. Add the tomatoes and chilli, season with salt, cover and cook for about 30 minutes. Cook the bucatini in a large pan of salted,boiling water until al dente, then drain and toss with the sauce in a warm serving dish adding the pecorino cheese.
Saltimbocca means "jump into the mouth". Place a half-slice of prosciutto on each escalope, put a sage leaf on top and fasten with a cocktail stick. Melt the butter in a fying pan and cook the veal over a high heat on both sides until golden brown. Season with salt, pour in the wine and cook until it has evaporated, then remove the cocktail sticks and serve.