Frijoles de la olla & refritos

Step 1: The night before, spread 1 ⅛ lb dried pinto beans on a tray and pick out any small stones or shrivelled beans. Rinse them, then cover with three times their volume of cold water and leave to soak overnight. Soaking shortens the cooking and helps them cook evenly so they don't split.

Step 2: Next day drain and rinse. Put the beans in a large heavy pot with half of ½ white onion in one piece, 4 cloves garlic and 2.5 litres of fresh water.

Step 3: Bring to the boil over a high heat and skim off the grey foam that rises in the first few minutes; it is just protein and makes the broth cloudy.

Step 4: Turn the heat down to a bare simmer, with just a few lazy bubbles, half cover and cook for 1–1½ hours. A hard boil knocks the beans about and splits their skins.

Step 5: Check every 20 minutes and keep the beans covered by 3 cm of liquid. Top up with boiling water from the kettle, never cold: cold water shocks the skins and makes them tough.

Step 6: Test a few beans. They are done when the skins wrinkle and peel back as you blow on a spoonful, and a bean squashes easily against the roof of your mouth with no chalky centre. Old beans can take up to an hour longer; keep going until they are there.

Step 7: Now add 2 sprigs epazote and 2 tsp salt and simmer for 10 minutes more. Salting at the end seasons the broth properly and stops it getting too salty as it reduces. The broth should be dark, slightly thickened and taste rich and beany.

Step 8: Fish out the onion. These are frijoles de la olla: ladle half into bowls with plenty of broth and top with 1 serrano chilli, 2 tbsp fresh coriander and a squeeze of 1 lime.

Step 9: For the refritos, heat 4 tbsp vegetable oil in a wide frying pan over a medium heat. Fry the chopped half of ½ white onion for 5 minutes, until soft and golden at the edges and smelling sweet. Add 1 chipotle chilli in adobo for a smoky version.

Step 10: Ladle in the remaining beans with about 200 ml of their broth. They will sizzle loudly; that is the frying that gives refritos their flavour.

Step 11: Mash with a potato masher or the back of a wooden spoon as they bubble, as smooth or as rough as you like.

Step 12: Keep cooking, stirring and scraping the bottom, for 8–10 minutes, until the beans turn into a thick, creamy paste that pulls away from the pan and leaves a clear trail when you drag a spoon through. If they get stiff or start to catch, add a splash more broth. They firm up further as they cool, so stop a little looser than you want.

Step 13: Taste both and adjust the salt. Store the pot beans in their broth (they dry out without it) and the refritos in a covered tub: both keep 5 days in the fridge or 3 months frozen. Reheat refritos in a pan with a splash of water or broth, stirring until creamy again.