My love of lentils and legumes of all sort goes as far back as I can remember. In recent years, the pinto has become my firm favourite among the beans, for it's a versatile legume of a gentle flavour that is easy to work with. The burrito use aside, the pinto is an excellent foundation for a bean salad, great in chili, and once you taste it baked with tomatoes, you will never want to eat Heinz again. And then there is the soup.
While I enjoy cooking, I don't always have the time for elaborate and time-consuming recipes. Fortunately good homemade food doesn't necessarily mean hours over the stove, and the pinto soup is an example of that -- it takes me under half an hour to make. The ingredients are simple, only the pinto beans, onion and chillies (fresh or crushed) are required, plus some stock; if you have carrots around, then they make a good addition, as does a bit of garlic, but you will get an excellent soup with just onion and chillies.
Being of the 'cooking is an art, not science' school of thought, I consider quantities mere minutia dictated by taste. But as a rough guideline, 400g of dry beans will make around three litres of the soup. For that I use two medium onions, and maybe a couple of larger carrots; chillies to personal taste.
Soak the beans over night (you can get away with less, but it impacts on the cooking time), then cook till soft -- using a pressure cooker hugely speeds this up. You will have to work out the exact timing for your pressure cooker yourself, but in ours, at 0.4 bar, pre-soaked pinto beans take 8min. Now, the secret to a good pinto bean soup is not to drain the cooking liquid, i.e., you should cook the beans in about as much water as you want in the final soup.
While the beans are cooking, chop the onion, not too fine, and fry it off with the chillies until nice and soft (I use rapeseed oil, I find the gentle flavour works well with the subtle flavour of the pinto). Add any garlic to the onion near the end.
Once the beans are ready mix in the onions, and any other ingredients, then add stock to taste (I quite like the Knorr stock pots, usually use one vegetable and one herb pot, but you might prefer something more wholesome and homemade instead). Bring to boil and cook (not pressure-cook!) for about 5min, or if using carrots, until they are soft.
That's it. As many foods, the flavour will develop if it sits for a time rather than being served immediately. It will keep in the fridge for a couple of days, or it can be easily sterilised in a kilner-type jar if you want to keep it longer, or there is not enough space in the fridge.