How do you roast sweet corn in husk in a microwave?

You just put the food in the microwave and the dish surface heats up as well as the food. Microwave heating work by heating the water molecules in the food. The dish contains a metallic content on the base which heats up. You can also preheat the dish and drop food into it so it starts sizzling straight away.

https://www.google.com/search?q=Corning+Ware+MW-11+instructions

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Incorrectly heat treated. Contact them for a warranty replacement.

The microwave burnt it. It will be a bit of trial and error with using your new microwave and will also depend (in this case) the brand of pop corn you've cooking. Check the recommendations on the pop corn packaging for time and heat range. Happy popping!

if only using on convection it is like any other oven so either metal or corning ware, if using with microwave it must be a microwave safe material like corning ware, which is also good for heat.

place a teaspoon of cooking oil in the pot and place on stove. Put a small amount of corn to be popped in the pot and the heat will do the rest. 1/4 cup of corn will probably overflow the pot so use small amounts first until you get the idea.

Most microwaves run high at default, if roast and reheat are given that is your high setting, take one cup of water and run for 1 minute in each setting, the water that is the hottest is the high setting.

You can order a replacement dish here. The dish shattered because the heat from the bag of popcorn was too much for it. If you look at the owner's manual for almost every microwave, they tell you not to put popcorn directly on the glass dish, but to put it on another plate.

The oven should be safe to use. Just look for any burned spots on the paint in the bottom of the cooking cavity.

The cavity thermal fuse may have failed. It is located on the top of the cavity.

Plug fuse may have blown. Replace that first or test.
Internal temperature trip may have cut out (if present)
Microwave generator (magnatron) may have failed.
Internal power supply may have failed due to moisture.

Very likely this machine is dead.
Save energy - and cash, by feeding birds stale bread and raw seed and corn.
Hopefully the next microwave oven will last longer.

The cost of repair may be more than the cost of replacement. Ask your nearest repair shop how much to replace the microwave unit, and check the power supply.

Sorry I can't offer a quick fix for you.