Despite its name, a rice cooker is a versatile kitchen tool that you can use even when you're not preparing a rice dish. While steaming vegetables is a common alternative use, you can also use it as a slow cooker. Whether you're using a microwave rice cooker or a standard countertop one, the principles of cooking remain the same -- low and slow heating to produce perfectly cooked ingredients. Dried mushrooms benefit from this method, as they are an incredibly flavorful ingredient, yet take time to completely reconstitute. A rice cooker, therefore, becomes the perfect means to cook them.
Pour the mushrooms into the large bowl. Fill the bowl with cold water and lightly rub each mushroom individually to loosen any grit or dirt clinging to the stem or cap. Rinse each one under cold running water before placing it in the colander.
Chop the mushrooms into the desired size, or leave them whole. Add them to the rice cooker. Pour enough water over the mushrooms to cover them by at least 1/2 inch. Cover with the lid.
Turn on the rice cooker if you're using a countertop model, as you would for white rice, according to the manufacturer's instructions. Depending on the model, you might only have one setting or several from which you can choose. Allow the cooker to automatically switch to the warm setting or manually switch it to this setting once the cooker turns off. Rice cookers automatically turn off or switch to the warm setting when the thermostat reaches a certain temperature. Leave it on the warm setting for 6 to 8 hours, or until you achieve the desired consistency. Add more liquid if desired, or if needed.
Insert the rice cooker into the microwave if you're using a microwave oven rice cooker. Cook for 5 minutes on full power. Reduce the microwave power to 50 percent and cook for another 15 minutes. Set it to the "keep warm" setting if available, or reduce the power to 25 percent, and cook for an additional hour.
Test to see if the mushrooms are ready by piercing them with a fork. If the fork easily slides into the cap and stem, then the mushrooms are ready. If not, cook for an additional 2 to 3 hours in the countertop rice cooker on the warm setting, or another 30 to 45 minutes on 25 percent power in the microwave cooker.
Remove the reconstituted mushrooms from the cooker and use in your favorite dish in lieu of fresh mushrooms. Store covered in the refrigerator and use within one to two days of reconstitution.