Kashiwa-mochi（柏餅/かしわもち）is a sticky rice cake with sweet bean jam inside, which is served around the Boys' Festival (端午の節句/たんごのせっく or こどもの日). Kashiwa stands for Daimyo Oak in Japanese and the cake is wrapped in a kashiwa leaf.
Here is the photo of Kashiwa-mochi that I prepared last year.
So here is the recipe for Kashiwa-mochi that I found at Tomizawa Shoten in Yokohama Sogo B2F.
There we can find various foods and materials for cooking, of course, the leaves of Kashiwa.
Easy version with a microwave oven
Ingredients for 10 servings
60g of shiratama-ko（白玉粉）*1
140g of Jyoshin-ko（上新粉）*2
15g of sugar
180g of water
200g of bean jam (smooth)
10 kashiwa leaves
Make 10 balls of bean jam (about 20g each)
Wash and dry briefly the leaves
1) Put the shiratama-ko and 180g of water in a pyrex bowl to melt together. Add the joshin-ko and the sugar and mix well until smooth.
2) Cover the bowl with plastic wrap and microwave for about 1 minute. Mix and knead the dough well.Cover with plastic wrap, microwave for 2 minutes and knead well. For the third time, microwave for 4 minutes and then put in some cold water.
3) When the dough gets cooled down, drain off the water, wrap in a wet (but wrung enough) cloth and make a ball with the dough. (If it is still too sticky, microwave again a little)
4) Divide the dough into 10 equal pieces and spread each to a oval shape and thinner in the center. Wrap a bean jam ball with the oval dough, then wrap a leaf over the cake. Attention: if the dough is not cooled down enough, the dough sticks to the leaf.
*1 Shiratama-ko is made from sticky rice. Here is the link to the Amazon research result.
*2 Joshin-ko is made from normal Japanese rice. Amazon search result.