Why it happens
A stew catches when the food at the base of the pan gets hotter than the rest and starts to stick and scorch. Thick stews, and those with starchy ingredients such as potatoes, lentils or flour, move around less in the pan, so the bottom layer stays in contact with the heat. A thin pan, a high heat, or a stew that has reduced too far all make it worse. If you catch it before it burns, the rest of the stew usually tastes fine.