Rich, thick split pea soup is a culinary masterpiece. Legumes such as peas are natural thickeners, and when you add potatoes to the mixture you should have a soup so thick that a spoon can almost stand up by itself in it. Sometimes, however, your adventures in cooking do not go as planned and you need to change your recipe or add items to the soup to rescue it from watery disaster. Fortunately, you have several options for thickening your split pea soup.
Cook the fresh or frozen peas by steaming them for five minutes over a stockpot filled with boiling water. When they are finished, the peas should be bright green and cooked through. Add the prepared split pea soup and the peas to a blender and puree the soup. Return the soup to the pot and heat for five minutes over medium heat, stirring constantly. The additional peas should thicken the soup.
Steam a large potato, peeled and cut into large chunks, over the stockpot for five to eight minutes or until the potatoes are tender and cooked through. Add the potatoes and soup to the blender and puree until the soup is smooth and creamy. The potatoes should further thicken the stock.
Add the flour to the soup and whisk it in. The flour is a last resort because it will change the texture of the soup and dull the pea flavor a little. Continue heating the soup over medium-low heat and whisking until the soup is your desired consistency.