1. Heat the oven to 200°C/180°C fan/gas 6. Put the squash into a non-stick roasting tin, tear over half of the sage leaves then toss with 1 tbsp oil and some salt and pepper. Roast for 25 minutes until golden and tender. With 10 minutes to go, add the pine nuts to one end of the tin.
2. Melt 25g/1oz of the butter with the remaining oil in a large pan. Add the leeks and garlic plus some salt and pepper, then soften for 5 minutes.
3. Stir in the rice, cook for 1 minute, then splash in the wine and boil until it has almost all disappeared. Keep the pan over a medium heat and stir in 250ml/9fl oz of the stock. Simmer, stirring occasionally, until the stock has been absorbed into the rice. Repeat three more times until the rice is creamy and tender. This normally takes about 20 minutes.
4. Take the pan from the heat. Stir in a few finely shredded sage leaves, the roasted squash, remaining butter, lemon zest, a squeeze of lemon juice and 50g/2oz cheese. Cover the pan then let the risotto relax for a few minutes. The rice should now be loose and creamy – if yours has thickened up, stir in a splash more stock. Season to taste with salt and pepper then scoop into bowls and scatter with the rest of the cheese and the pine nuts.
Tip: For a special finish, heat 2 tbsp oil in a saucepan, then add a few sage leaves. Fry till crisp, drain on kitchen paper, then scatter over the risotto to serve.