These are sakura mochi. They are only available around Sakura or Cherry Blossom time. I was able to find them at my favorite Japanese store. They are imported from japan yet tasted very fresh. The pickled cherry leaves have a light salt y taste ( like o^ mai) which adds a surprising flavour to the sweet mochi. I am so glad I tried them!
Now I'll have to find the sakura-yu or tea made from salt preserved cherry blossoms which 'bloom' again in the tea into pretty pink blossoms. If you know where to get them in the bay area or by mail order, please leave a note in the comments, it will be much appreciated!!
My quest for sakura-yu hasn't been very successful, however I found a couple of recipes which I save below, in case I get too desperate :) and decide to make my own.
Sakura no hana tsukeru (Preserved Sakura Blossoms) and Leaves - how to's found on Egullet.com
Choose fresh, soft, young leaves that have just reached a reasonable size.Prunus lannesiana var. speciosa, the large-flowered single "Oshima" cherry has large leaves and plenty of fragrance, which apparently comes from toxic substances which make you feel good...right up until the point where you pop your clogs, that is! ... Several other varieties are related to this, including the fairly popular greeny-yellow "ukon" variety. The Oshima cherry family have soft leaves, but you can still pickle other cherry leaves and either chew harder or just use them for flavoring.
J site on preserving cherry leaves.
http://www.ajiwai.com/otoko/make/sakura.htm
To summarize: 1 part by weight of fresh cherry leaves, weighed. 20% of that weight in coarse salt such as kosher salt. 1 part by weight of uncolored or "white" ume-su, the briny vinegary liquid that seeps from umeboshi as they are first pickled. You can also buy it bottled, and if you have none, make a brine of 5 parts water to 1 part salt by weight.
Wash leaves, put in a colander in a big bowl, pour boiling water over them, drain, and refresh quickly in cold water. Remove excess water, for example using a salad spinner.
The text talks about putting the leaves in the bottom of a cake tin, but that's asking for rust! I'd use a tabletop pickler, or a casserole which you can fit some kind of plate or board inside. Lay leaves out so that you can easily sort them by size (helpful when you want to make sweets etc). Spread 1/3 of the salt in the bottom of the container, fold leaves in half vertically, and lay in the container, then sprinkle the remainder of the salt over. Here she just shows 10 of the leaves.
Pour over the ume-su or the cooled brine. Spread wrap over the top (press firmly to exclude as much air as possible). Put a plate or board on top, and add weights - rocks, a stack of plates, a jar etc. Text doesn't say, but use 2-3 times weight of leaves at least. Store in a cool dark place or in the fridge, and after 2-3 days, when liquid has been exuded, reduce weights by half.
Text doesn't say, but I think after a week or so, you can take the weights off and put them in a plastic container, preferably with wrap pressed over the surface.
For salted cherry blossoms, you want blossoms with a nice long stem, heavily double. I won't give you a botanical name, as several varieties have double-flowered cultivars. (A variety of this particular sakura is Prunus serrulata "pink cloud".)
J page with photos of salted blossoms
http://www5b.biglobe.ne.jp/~bon-c/kan7-2.htm
and recipe
http://www.agri.pref.kanagawa.jp/nosoken/NOUSANKAKO/Sakurahanatuke100g/Sakurahanatuke100g001.htm
This site doesn't give exact quantities, but 20% by weight of coarse salt in proportion to the blossoms would be about right.
Again, rinse blossoms gently, drain water, lay in salt, sprinkling some over the top, and press under weights for about 3 hours. Gently squeeze most of moisture out (use kitchen paper), and put in a jar with white ume-su or a 20% brine and white wine vinegar solution. Leave for a week.
Drain and again squeeze gently. Shake petals loose a little, and store in coarse salt - will keep almost for ever.
Oh yes, another version: cherry blossom salt, which I tell you shamelessly that I read in a magazine at the bookshop the other day.
2 cups cherry blossoms
2 tab coarse salt
Preserved cherry leaves if desired.
Chop cherry blossoms finely into salt, ditto leaves if desired, mix well into salt, and use as desired - for example, on seki-han.
I'm planning to try this with our remaining ume blossom, if it would stop raining long enough for me to get some!
--------------------
Helen in Japan
And last but not least, here is a beautiful close-up photo of a cup of sakura tea from http://www.trekearth.com/gallery/Asia/Japan/photo45957.htm