Trim the turnip tops, removing the larger stalks and ribs; if using sprouting broccoli, cut the larger pieces in half. Wash well. Peel the onion, cut lengthwise in half and slice thinly.

Place the turnip tops or broccoli in a large, heavy-bottomed fireproof casserole dish, add the onion, stock, a pinch of salt of 3-4 black or white peppercorns. Bring to the boil, cover and simmer gently for 15 minutes (10 minutes for broccoli).

Sprinkle the olive oil all over the turnip tops, turn up the heat and cook uncovered for up to 10 minutes (broccoli will need only about 5 minutes), or until the turnip tops are done but still have a little bite left to them.

Serve with the reduced cooking liquid as a sauce, and eat with slices of semi-hard cheese and wholemeal bread.