Preheat the oven to 160°C.
Peel the vegetables. Chop the onion, cut the parsnips lengthwise, then in half. Cut the carrots in half and chop the squash into bite-sized pieces. If the potatoes are big, cut them in half.
Add some oil in a large, heavy-based casserole dish, then gently soften the onion. Add the sage leaves and stir for 2 minutes. Sprinkle the meat with a little cornflour (about 1 or 2 teaspoons), then add to the onion and stir for a few seconds.
Add the tomato purée and pour in the wine and stock. Season with salt & pepper, then bring to the boil.
Cover the casserole dish with a lid or foil and put it in the middle of the oven. Cook for about 3 hours (depending on the quality of the beef). It’s ready when the meat is tender, the sauce is thick and silky (do check after 2 hours of cooking).
Mince the garlic and finely chop the rosemary leaves. Using a pestle &mortar mix the rosemary, lemon zest and garlic into a rough paste.
Serve the stew with the rosemary gremolata sprinkled on top.