Melt 1 tablespoon of the butter in a large saucepan over medium heat. Add the onion and bell pepper and sauté until softened, about 5 minutes. Add the potato and 1 cup of broth. Bring to a simmer, cover, and cook until the potatoes are just tender, 10-15 minutes. Stir in the remaining ½ cup broth, water, corn and cream. Bring to a simmer. In a small bowl, combine the flour and remaining tablespoon butter using your fingers or a fork. Stir into the soup and stir constantly until it returns to a simmer and thickens slightly. Heat the olive oil in a heavy skillet and brown the sausage over medium-low heat, 4-5 minutes. Stir sausage into soup, season with salt and pepper, and scatter cilantro over the surface.