The first time I had mochi, I was eighteen years old and also had sushi for the first time.  The sushi experience was not something I enjoyed at the time but the mochi was.  It was only slightly sweet but oh so pillowy soft and chewy.  At first it was a stunned moment because I had expected the sweetness of powered sugar on the outside.  The slightly coarse powdery texture of the cornstarch threw me off and at first my mind rejected what I was tasting (the same thing happened with the sushi too.  It was all I could do to keep from gagging even though it didn't taste bad.  My mind kept screaming "RAW FISH RAW FISH" but my taste buds were like "simma down, it's all good").  The initial knee jerk reaction went away in microseconds.  I couldn't get enough of it.  Unfortunately it would be years before I had it again.
Actually it wasn't until I moved to San Diego in the mid eighties that I ran into again.  A friend took me to the local "asian" store on Convoy ave and they had some there in one of the restaurants.  It wasn't like I remembered and couldn't figure out why.  Years later when I began to work in the area and started to visit all the different asian restaurants did I realize the problem.  The softness was there but it was that super soft, chewy goodness that I was looking for. A friends mom made it one day, well actually she was cutting it up while I was over and she let me have some.  It was then that I learned that she always lets it sit overnight.  Without the overnight factor,  you do not get that super soft, chewy, eyes rolling back in your head reaction.  That could just be me but I think you understand.  Let it sit overnight.
I've now been making it for several years and try different flavors all the time.  I love this black cherry one though, it's one of my favorites.  Any time that I use juice, I always concentrate it.  It doesn't make it a really strong flavor but still gives it a wonderful taste.  I've tried before without concentrating the juice and to me the flavor is lost.
Try this recipe, it is actually quite easy and the final 
Recipe:

1 lb Glutinous Rice flour
2 cups Sugar
2 cups Black Cherry Juice (After reduction)
1 can coconut milk, unsweetened
1 cup cherries, they do not have to be pitted (fresh or frozen)
1 cup CornStarch

Heat oven to 275 degrees F or 135 C,
Dish 13 x 9 
Aluminum foil
Spray oil

I used a 32 oz bottle of Black Cherry Juice and poured it all into a sauce pan.  Set the heat to medium low and add your cherries.  I let it reduce for just over 2 hours.  
Pour through strainer.  Then push the pulp around until you get out as much juice as possible
Add to large Bowl.
Add coconut milk, sugar and rice flour and mix
Preheat oven to 275 degrees F or 135 degrees C.
Line a 13 x 9 pans, or smaller but you will need more pans.  It should only be 1/2 thick or less when you pour it in otherwise it does not cook in the middle.
Line the pan and spray generously with the oil
Pour in the mochi liquid and cover with a piece of foil that is also sprayed with the oil.  The foil should be touching the surface of the liquid.
Place in oven and cook for 90 minutes
Remove and let cool at least and hour
Carefully peel back the aluminum foil and replace it with a fresh piece that also has been sprayed with the oil, again touching the surface.
Now here is the hard part.  Leave it alone for 12 hours at least.  The mochi will be pillow soft.
After the 12 hours, Gently and I mean gently pull off the top aluminum foil.  Then turn it out on to a board that is covered with the cornstarch
Use a plastic knife, I'm not kidding here, and cut off the edges.  I eat these while I'm cutting up the rest.
As you cut, dip it and coat each piece in cornstarch
Consume, you can also wrap in waxed paper or seal airtight, it will keep for a few days
Be careful, do not feed to young children as there is a choking hazard.  This is really soft and chewy.  It is recommended that when given to the "old" or young to cut it into small pieces to reduce the choking hazard.

Picture
Push as much of the juice through as you can. Then discard what is left in the sieve.
Picture
I use heavy duty aluminum foil on the bottom, remember to spray oil very well. It needs it or it will just stick.
Picture
It looks very strange coming out of the oven and not what you expect. Don't worry, it worked.
Picture
Gently lift off the foil
Picture
Cut with a plastic knife, all others will stick. On occasion, throw down some more cornstarch so the slab doesn't stick
Picture
Awww, look at these beauties. So soft, so pillowy, so much goodness. This pictures only shows what a full batch makes. It makes a lot and I mean a lot. I've never counted but may be a hundred squares.
I hope you enjoyed this recipe.  If you did, leave a comment below.  I also have a YouTube channel where I feature many of my recipes.  If you would like to check it out, click on this link:  Bristlee One

Thank you for stopping by and remember, enjoy life.
It's the one you have,
Tammie