I have actually never eaten "traditional" mochi - but traditionally, when I was growing up, we bought flat cakes of Grainnaissance raisin-cinnamon mochi and baked it till it puffed up in the toaster. Such a delicious tradition!
Now we're eating rice again, but only if it's white or fermented (if it's brown). The folks at Grainnaissance confirmed that they don't ferment their rice, so I was determined to make my own mochi.
The biggest problem with trying to make mochi, in my previous experience, is that you will burn out the motor of your blender or food processor if you try to "pound" the cooked sweet rice this way. Trust me - I've tried it.
Recently, I found some useful information online from someone who grinds their rice _before_ cooking it. I have now refined my technique, and while it does require a Vitamix or similar high-powered blender, it _works_, does not burn out your motor, and you can create a nice flat square cake of mochi that can be chilled/dried and then baked till it puffs up. I'm sure you can do other things with it, such as eat it immediately, but I'm just happy to recreate my family's tradition. :)
450 g. sweet/"glutinous" brown rice, soaked according to these instructions, and drained http://lifeisapalindrome.com/recipes/how-soak-brown-rice
Between 1/2 and 3/4 c. water (as little as you can get away with)
1 tsp. salt
3/4 tsp. cinnamon
Scant 1/2 c. raisins
Preheat the oven to 350f.
Process all ingredients in Vitamix on "high" until the mixture becomes sandy and mostly pulverized (use the pusher thingy to make sure that things are moving down as they should, while the motor runs). This takes about 2 minutes.
Pat the mixture into an ungreased glass 8x8" pyrex pan or similar. Now, place the 8x8" pan into a larger baking dish, and fill the larger baking dish with water ~1 inch deep. This creates a water bath. Now make sure that you can cover the larger baking dish (or use aluminum foil), so that the mochi in its pan inside will steam.
Carefully transfer the dish to the oven; bake for an hour and a half.
Carefully remove dish from oven, and remove mochi (still in its pan) from the water bath. Once the mochi has cooled, place the whole pan into the fridge - after it chills overnight, it will release from the pan fairly easily. Until then, it won't!
Once the mochi has cooled and dried a bit (overnight or longer), remove it from the pan. At this point, you can store mochi cakes in the freezer, or you can proceed with eating it for breakfast.
Cut the mochi into ~1-inch squares. Place squares on ungreased baking sheet, and bake at 450F for 10-15 minutes, or until mochi puffs and turns golden brown.
Eat! Traditionally. :)