For the beans:
- 450gms/2.5 cups of black beans
- 5 cups water, more if needed
- 1 ounce dried porcini mushrooms, rinsed and minced
- 2 bay leaves
- 1 teaspoon salt
- 0.5 teaspoon baking soda
To make the soup:
- 3 tablespoons olive oil
- 2 large onions chopped fine
- 3 celery ribs chopped fine
- 1 large carrot, peeled and chopped fine
- 6 garlic cloves minced
- 1.5 tablespoons of ground cumin
- 0.5 teaspoon red pepper flakes
- 6 cups vegetable broth
- 2 tablespoons cornstarch
- 2 tablespoons water
- 2 tablespoons lime juice
- salt and pepper
For the beans
Put the beans, water, mushrooms, bay leaves, salt and baking soda in a large saucepan. Bring to the boil and skim any stuff off that comes to the surface. Cover, reduce heat to low and simmer gently until the beans are tender – maybe 1.25 to 1.5 hours. If still not done, add some more water and simmer some more. When ready remove the bay leaves but don’t drain!
For the soup
Heat oil in heavy pan until shimmering. Add onions, celery and carrot and cook until softened and slightly browned – 12 to 15 mins.
Stir in the garlic, cumin and pepper flakes and cook until fragrant – about 1 min. Stir in the broth and cooked beans with their cooking liquid and bring to the boil. Reduce heat to medium low and cook uncovered stirring occasionally until flavors have blended, about 30 mins.
Puree 1.5 cups of beans and 2 cups of liquid in blender until smooth and then return to the pot. Whisk cornstarch and water together in a bowl then gradually add half and see how it thickens after 3 to 5 mins. Add the rest if not thick enough.
Take off the heat and add the lime juice and salt and pepper to taste.