1/8 cup black sesame butter (black tahini)
2 tablespoons agave nectar
2/3 cup coarsely ground black sesame seeds
1/8 cup peanut butter Outside Covering:
1 1/2 cups glutenous rice flour
1/2 cup sugar
1 1/2 cups water cornstarch, as needed
1. Prepare filling before making the outer covering. Once the covering is made, you'll need to work really quickly to fill the mochi, since it becomes hard to work with once it cools off too much. Mix black sesame butter, agave, ground sesame seeds, and peanut butter thoroughly with a spoon.
2. Mix the flour and sugar well; then mix dry ingredients into the water. Make sure you mix thoroughly or else your mocha will be lumpy! Once everything is well mixed, microwave the mixture (preferable in a glass or ceramic bowl) on high for about 4 to 5 minutes.
3. Once done, mix it until it seems uniform and put it back in the microwave for another 4 to 5 minutes and mix when done. At this point, it should be nice and stretchy, if not, stick it back in the microwave for another 2 minutes. After the 3rd time microwaving the glutinous rice batter, you're ready for the filling!
4. Here you have to work quickly because the batter becomes hard to work with once it cools down. Coat work surface with plenty of corn starch this will prevent it from sticking to it. Pour your batter out on to work surface coating the surface of your batter. Take either a rolling pin or use your hands to flatten it out.
5. When flattening out batter, throw on more cornstarch to prevent any additional sticking that might happen. Once batter is about 1/8" thick, start cutting it into little squares, then put dollops of filling in the center. The way I like to fold the mochi up is by bringing corners that are diagonally across from each other to the center and then pinching the edges closed as they meet, but that's not the only way to do it! Find what works best for you!
The sky is the limit really for what you want to use as your mochi filling! Ariel made a nice mocha with boysenberries and almond butter;so good! For covering, you will notice that the ratio of flour to water is 1 to 1 1/2, so if you want to make more, it should be fairly easy to scale up. The covering makes a plain tasting outer covering (but still really good). If you want to spiff it up you can add extracts or other things. One thing that I like to do is brew tea in the water that I mix with the flour. Happy Eats!
This recipe is also posted to my vegan blarg! http://www.aveganblarg.com/2011/06/mochi.html 
Source of recipe: The covering for this recipe I got from http://allrecipes.com/Recipe/microwave-mochi/Detail.aspx  but I experimented with the fillings!