Are you making a traditional lasagna filled with layers of creamy béchamel? Maybe you are cooking a quick beef and Chinese broccoli stir-fry for dinner with a sauce that’s loaded with ginger and garlic? Or perhaps you’re considering making a sweet, thick vanilla pastry cream to fill a fruit tart this weekend? In most cases, the secret to a thick sauce (or filling) that coats food evenly is starch, whether plain flour, cornstarch, tapioca starch, or even arrowroot starch.