2 cups cooked cannellini beans, rinsed and drained, divided
1⁄2 cup chopped fresh basil
1 Tbsp chopped fresh oregano
1 tsp sea salt
Freshly ground black pepper
Heat the olive oil in a large, heavy saucepan over medium heat. Add the leaks and cook, stirring frequently, until golden and soft, about 5 minutes. Add the garlic and cook for 1 minute, then add amaranth, stock, bay leaf and tomato paste and bring to a boil.
Reduce heat to a simmer. Cover and cook for 30 minutes.
Remove the bay leaf from amaranth mixture, add 1 cup of the beans and use a handheld blender to puree in the pot until smooth. (Alternatively, puree the beans in a food processor, add the amaranth mixture – working in batched if necessary – and puree again until smooth, then return to the pot.)
Stir in the remaining beans, the herbs and the salt. Warm gently just to heat through. If desired, thin the soup with additional stock (heat before adding to avoid overcooking the soup). Season with additional salt and pepper to taste.