A slurry is a mixture of starch and liquid stirred together until the starch dissolves. They’re used to thicken soups, sauces and stews. Combining the starch with just enough liquid to form a thin paste makes it easier to incorporate the slurry without lumps.
You can use water, stock or any liquid that will complement your dish. Once you add the slurry, heating your food will activate it. Take it off the heat as soon as your food thickens. Overcooking your slurry can cause your sauce to lose its thickness and thin out.
A slurry made with flour requires a longer cooking time to activate its thickening power and to cook out the raw flour taste. Cornstarch has twice the thickening power of flour and works almost immediately after heating.
Give your slurry a stir just before using to keep the starch from settling at the bottom of your bowl.