Most people think of a microwave as an inferior form of cooking. The microwave is just an appliance that sits in the kitchen until you need to pop something to heat for a few minutes. I’m not going to claim that the microwave is the best cooking utensil but if used properly the microwave is more hand than you think. The important thing is to know exactly how to properly use a microwave and that includes knowing what kind of dish to use when inserting food into the microwave.
When choosing the right microwavable dish there are three different dimensions to consider. What is the depth of the dish? What is the slope of the dish? What is the shape of the dish?
We’ll start with the depth of the dish. Often when microwaving some sort of meal that comes in a dish or tub of some kind has instructions that will say to stir once halfway through. It is important to stir the food halfway through because the heat is coming at the food from the top and the sides but the food underneath is not being heated the same amount as the food on top.
That means if the dish is deep and there are several layers of food then it will be necessary to stop the microwave multiple times to mix the food and make sure the food at the bottom is also heated. The solution to this is to use a dish that is shorter in depth but wider in length. If the food is essentially one layer then all of the food will heat at the same time.
The second consideration is the slope of the microwave dish. Some casserole dishes are more about looking fancy than being a good utensil for heating. There might be a dish where the sides of the dish slowly widen as it gets to the top forming sort of a lip on the sides instead of just a straight edge. When microwaving a sloped dish the food that is on the lip will cook faster than food next to it and that food will cook faster than the food directly next to it and so on. To have a nice evenly cooked meal be sure to use a dish that has straight edges.
The last concern is the shape of the dish. Most dishes will either be square, rectangular or round. When microwaving a dish there are microwaves coming at the food from all directions, including the sides. If a dish is square or rectangular that means in each of the four corners those corners have waves coming from both sides of the corner. This is going to lead to that part of the dish getting more heat and the result will be corners that are cooked a lot more than the rest of the meal. Round dishes are preferable because there are no corners and all of the edges will be cooked properly.
The best shape for a dish though is a ring (think of something similar to an upside down jelly mold). The only problem with a round dish is that even though the edges will be heated even, the middle of the dish is not getting as much heat as the sides. If there is a hole in the middle of the dish from the ring then both the outside edge and the inside edge will cook evenly.