First, make some rosemary oil. Put 80ml extra-virgin olive oil and the rosemary leaves in a small pan on a low heat for four to five minutes, until bubbling, then take off the heat and leave to infuse while you make the rest of the dish.
Put five tablespoons of oil in a large casserole pot on a low-medium heat and, when hot, add the onion, carrot and celery and cook, stirring occasionally, for 12 minutes, until softened. Add the garlic and tomato paste, stir for 30 seconds, then add one of the tins of chickpeas and all the water from the can, and mash with a potato masher until you have a rough paste.
Stir in the preserved lemon and the second tin of chickpeas and its water, then add the pasta, a teaspoon and a half of salt, the chilli, and a litre and a half of tap water. Stir to combine, cover the pan and leave to simmer until the pasta is cooked – it could take a bit longer than the packet suggests (mine took 15 minutes).
Stir in the nutritional yeast and black pepper, simmer for a final three or four minutes, then divide across four bowls, drizzle the rosemary oil on top and serve.
