kashiwa

It's also served for Boy's day, I think with the idea that the kids should grow strong and tall like an oak tree.
It can be made very easily, or very sophisticated with wheat starch (see recipes below).
FIlled with either 粒あん or 味噌餡 (like the 花開もち). I suppose it'd taste also nice with my beurre noisette 味噌餡.

Recipe

For 6 pieces

90 gr 上新粉
10 gr 白玉粉
80 gr water

Mix, knead, then steam in pieces on a cloth for 15'. Knead in すり鉢, then place into cold water for 1'. Dry and put back.

7.5 gr sugar
5 gr wheat starch (浮粉 in Japanese). It can't be other starches like potato or corn!
15 gr water

➡️ They dry out quickly (overnight), so I thought adding some 5 gr of glucose syrup here might be a good idea.

Add the syrup bit by bit to the dough while kneading it.
Moisten your hands (but not too much) to work the dough. 30 gr of dough wrapped around 20 gr of 中餡.
In the 淡交テキスト, they form balls for the 粒あん and 蛤 (clams) with the 味噌餡. The latter, however, is tricky to get right, so if it had to look perfect, I'd use 粒あん.
These turn out to be a bit difficult to eat, they are quite sticky. It's easiest to just fold the leaf back and eat them like a どら焼き.

Easy Recipe

This is from 金塚. It's much easier and tastes fine, but it's also not nearly as sophisticated in terms of texture. However, I think they're less sticky, so that might be a benefit.
100 gr 上新粉 (or just plain rice flour)
10 gr sugar
150 gr 50° C water

Knead and steam in cloth (it's quite runny at first) for 15'. Then knead in baking sheet.