Ajillo oil is a delicate and delicious chilli condiment. It is made with garlic and guajillo, a mild dried chilli known for its fruity flavour and for staining food with its deep, brick-red colour. In Mexico, the oil is used to season seafood dishes, but I find many uses for it in my kitchen when I’ve made a batch. Here, I toss chestnuts in it and use it to drizzle over an autumnal risotto; the roundness of the chilli and garlic make a bewitching contrast to the sweetness of the squash. Squash risotto with chestnut chilli oil Roasting the squash or pumpkin first adds a huge amount of flavour to this risotto, but you could steam it instead. Prep 10 min Cook 1 hr 10 min Serves 2 1 medium squash or pumpkin (about 800g), skin left on and thickly sliced 5-6 tbsp olive oil A handful of thyme sprigs, leaves only Salt and black pepper 1 large white onion, finely diced 350g pearl barley 200ml white wine 1 litre vegetable stock 60g parmesan or grana padano A knob of butter Chopped parsley, to serve (optional) For the chestnut ajillo oil 3 guajillo chillies (or use Spanish nora peppers instead) 300ml sunflower oil 3 large garlic cloves, finely chopped 150g cooked chestnuts, roughly chopped 1 tsp chilli flakes (optional) Juice and zest of ½ lemon Heat the oven to 200C (180C fan)/390F/gas 6. Toss the squash with two tablespoons of the olive oil, a third of the thyme and season generously. Transfer to a baking tray and roast for 30 minutes until soft and turning golden brown at the edges. Set aside. For the ajillo oil, remove the stalks and seeds from the chillies. Cut the chilli into rings with scissors. Warm the sunflower oil in a small pan, then turn the heat to its lowest setting and add the chillies, garlic and half the remaining thyme. Add half the chestnuts and cook on a low heat until the garlic has turned pale golden – five to 10 minutes. Roughly blitz the oil with a stick blender while it’s still in the pan, then add the rest of the chestnuts and the chilli flakes, if using, leave to warm through, then turn off the heat, stir in the lemon zest and juice, and set aside. The oil will last a few weeks stored in a sterilised jar. To make the risotto, warm three tablespoons of the olive oil in a wide pan and add the onion. Season generously, add the last of the thyme and sweat over a medium-low heat for seven to eight minutes until soft. Turn up the heat to medium, add the barley and stir until it glistens in the oil. Add the wine, stir until it has been absorbed, then add the stock one ladleful at a time, stirring until it is absorbed before adding more.After 10 minutes of cooking the barley, scrape the squash from its skin and add it to the risotto. Continue to cook, adding stock until the barley is tender but still with some bite, about 20 minutes. Add the cheese and butter and stir to combine. Season to taste. Serve the risotto in bowls with the ajillo oil on top and some chopped parsley. The simple flex You can easily leave out the butter and cheese here – the chilli oil packs enough of a punch without them.