Things You'll Need
Small microwave-safe bowl
Cornstarch is obtained from the kernel of the maize plant.You can use it in cooking as a thickening agent for liquids such as sauces, gravies and broths. If you add too much water or broth to a soup, you can use cornstarch to thicken it to your preference. Using cornstarch, you can transform soup with broth no thicker than water to a gravy-like consistency, and anywhere in-between. Thickening soup with cornstarch requires approximately 15 minutes.
Pour 3 tbsp. water into a small bowl for every 3 cups of soup you need to thicken. Microwave in 15-second increments until it boils.
Add 4 tbsp. cornstarch to the boiling water for every 3 cups of soup. Whisk the cornstarch into the water until it forms a smooth consistency.
Pour the water and cornstarch mixture into your soup and stir with a wooden spoon for 60 seconds. Simmer the soup for 15 minutes over low heat.
Sample the soup's broth. If it is not thick enough for your taste, make a second batch of water and cornstarch and repeat the process.
If you do not whisk the cornstarch into the water completely, it will create tasteless lumps in your soup.