Preheat the oven to 160ºC/300ºF/gas 2.
Peel and roughly chop the onion, peel and quarter the parsnips and peel and halve the carrots. Deseed and roughly dice the squash. Pick the sage leaves.
Heat a little oil and the butter in a casserole pan on a medium heat, add the onion and sage leaves, then fry for 3 to 4 minutes.
Meanwhile, toss the meat in a little seasoned flour, then add it to the pan with all the vegetables, the tomato purée, wine and stock, then gently stir together. Season generously with black pepper and just a little sea salt.
Bring to the boil, place a lid on top, then place in the oven until the meat is tender