Mochi is Japanese sticky rice cake used both in savory and sweet dishes.  Mochi is usually made from sweet rice (also called Mochi rice) cooked and pounded until it becomes a paste that is very sticky and smooth, then formed into cakes or blocks.  It is often eaten in New Year’s Ozoni soup or baked with soy sauce.  Mochi made from cooked sweet rice doesn’t stay fresh and soft too long, and usually needs to be cooked to be able to be eaten again.  However, here we made Sweet Mochi using Mochiko (sweet rice flour) and a lot of sugar, and it is pliable for an extended time to be able to shape it in the way you want for desserts.
We used Mochiko which is basically powdered sweet rice. It becomes Mochi by adding water and steaming.  Because it is a powder, it is easier to have Mochiko in your pantry longer and it is much simpler to use to make Mochi than rice.  Mochi from Mochiko may seem softer than traditional Mochi, but it stays soft from adding sugar.  It has a lot of sugar, and it is quite sweet.  You could cut some of the sugar if you will eat it right away, however, the texture and shelf life may suffer a bit.
With this Sweet Mochi, you can make many varieties of Japanese sweets.  You could wrap a ball of Anko (sweet red bean paste) with Mochi and make it into Daifuku Mochi, put ice cream inside to make Mochi ice cream, or just as is coated with some Kinako (soy bean powder).
Ingredients are simple enough. Mochiko is often available in regular supermarkets in the US  (Mochiko can be used as a thickening agent).  The steps of making it are easy too.  Just take care dissolving sugar. We suggest adding the sugar in parts and to dissolve completely and evenly. It is easier and tastier than you may think to make Japanese Sweet Mochi at home, so try it !

• 1 cup Mochiko (sweet rice flour or Mochi flour) (160g)
• 3/4 cup water (180ml)
• 2 cups sugar (400g)
• cornstarch
• Anko (sweet red bean paste) or
• Green Tea Ice Cream if you want

1. Mix Mochiko and water in a glass (or other heat proof) bowl and mix well. Add some more water if it's too dry, 1 Tbsp at a time.
2. Steam the Mochiko dough (leaving the dough in the bowl) in a steamer for 20 minutes.
3. Transfer the steamed Mochi into a pot and cook at medium to medium low heat with 1/3 of the sugar (2/3 cup). When the sugar is completely dissolved, add another 1/3 of the sugar and mix well. Add the last part of the sugar and cook some more until the sugar is dissolved. Take the time to melt the sugar, but be careful not to burn it.
4. Take the hot Mochi out from the pot onto a sheet pan liberally dusted with cornstarch. Shape as you like. 

source :  http://www.japanesecooking101.com/sweet-mochi-recipe/