To thicken the Navy Bean Soup, I suggest that you remove 1 cup of beans and mash with a masher, immersion blender, or purée in a food processor or blender until smooth. Return mixture back to the soup and stir to combine. The natural starch from the beans will act as a thickener. If you prefer your bean soup to resemble more of a stew, you can mash more of the beans to thicken it even further!