If you'd like to thicken it up while still hot, there are a few ways you can do so! Note: This soup will continue to thicken as it cools down. -The first method is to smash up a few more of the potatoes in the soup. The starches in the potatoes will immediately help thicken the broth. -The second method is to add 1-2 tablespoons of all purpose flour to the soup. To do this, you'll want to form a slurry by mixing 3-4 tbsp of the broth per 1 tbsp of flour. Then, pour the slurry into the soup and simmer for a few minutes to cook the flour.