Oat gruel soup is not exactly a culinary delight, but the best thing to eat when you have a stomach upset. Salt is returned to the body through the broth. The broth also strengthens the body and helps you get back on your feet more quickly. Melting flakes make the soup slimy and the stomach can digest it more easily. Pour water into a pot. Add a slightly heaped teaspoon of broth and oats Melt Flakes. Bring the oat gruel soup to the boil while stirring. Switch to low temperature. Simmer oat gruel soup until it thickens. If you don't like oat gruel soup prepared this way, try the recipe for milk soup.