Your gravy is lumpy Result: Lumpy gravy. Next time, whisk wisely. Meanwhile, here's a fix. One cause is the direct dumping of dry flour, cornstarch, or other thickener into the hot stock or broth. Another: adding broth too quickly into a roux—the flour-fat mixture that some gravy recipes start with—which can cause clumping or a gluey layer on the bottom of the pan. Hot spots in a large pan can complicate things, as well. In any starch-based sauce, the thickener needs to be gradually introduced