Preheat the oven to 220 °C (425 °F) Gas 7.
Put the squash, onion, sage, 1 tablespoon of the oil and some seasoning in a roasting tin, toss well and roast for 30 minutes, or until the vegetables are golden and cooked through.
Heat the remaining oil in a large frying pan and gently fry the garlic, chilli flakes and a little seasoning for 2-3 minutes until soft, but not browned. Add the pine nuts and stir-fry for 2-3 minutes until lightly browned. Add the roasted squash, onions, sage and the feta, and stir well until combined. Serve at once.