STEP 1Heat the oven to 220C/200C fan/gas 7. Toss the squash in 1 tbsp oil together with the chopped sage. Scatter into a shallow roasting tin and roast for 30 mins until brown and soft.
STEP 2While the squash is roasting, prepare the risotto. Bring the stock to the boil and keep on a low simmer. In a separate pan, melt half the butter over a medium heat. Stir in the onions and cook gently for 8-10 mins until soft but not coloured, stirring occasionally. Stir the rice into the onions until completely coated in the butter, then stir continuously until the rice is shiny and the edges of the grain start to look transparent.
STEP 3Pour in the wine and simmer until completely evaporated. Add the stock, a ladleful at a time, and stirring the rice over a low heat for 25-30 mins, until the rice is cooked al dente (with a slightly firm, starchy bite in the middle). The risotto should be creamy and slightly soupy.