Step 1: Watch Your Fingers !
First, collect what is needed :
A sharp knife
A microwave safe plate
A microwave oven
A clean cloth to hold the hot chestnuts
A match or a lighter
With the aid of the knife make a cut on a side of each chestnut : this will prevent your chestnuts from exploding when in the microwave.
Forgetting to do so is probably not dangerous but having to clean the microwave is definitely a hassle you don't want !
Step 2: Microwave.
Step 3: Alcohol, Please !
Use the cloth to hold them.
Put the chestnuts back on the plate and pour some Grand Marnier on them.
Step 4: Flambe'
Be careful as the hot chestnuts and GrandMarnier will develop flammable vapors.
Alcohol will burn out, so the recipe is reasonably good for children also.