That's why you lower the power. Leave enough time for entropy to distribute the heat before dumping more energy into the food. The more heterogenous the food is, the more you need to lower the power (down to maybe even 200-400 W for mixed leftovers). And make sure all your foodstuffs are touching each other to allow heat to homogenize.
Except the food has localized concentrations of oil, fat or water or differences on overall density.
That's why you lower the power. Leave enough time for entropy to distribute the heat before dumping more energy into the food. The more heterogenous the food is, the more you need to lower the power (down to maybe even 200-400 W for mixed leftovers). And make sure all your foodstuffs are touching each other to allow heat to homogenize.