June except for 京都, where they have it all year around.
金塚's 外郎-based recipe, which I prefer much more to the gooey wheat flour mess that is the other recipe:
外郎
100 gr sugar
200 gr water
1 gr salt
120 gr 上新粉 (or 上用)
Glue
20 gr 葛
50 gr water
40 gr sugar
100 gr 甘納豆
Make a syrup of the first 3 ingredients, mix with rice flour. Separately, mix glue ingredients, sieve and cook until thickened. Add the 外郎 bit by bit to that.
Pour 80% of that liquid into baking sheet-lined 流し器, steam for 7'; then add the rest (and then the 甘納豆))
♟️ Next time, I want to make a chess themed one with black and white beans.
Other recipes
From the 淡交テキツト
Mix 80 gr white flour, 16 gr joushinko, 150 gr sugar with 250 gr water
Mix 5 gr kudzu with 50 gr water
Combine, then put into a baking sheet lined container, but keep about 30 gr mixture for later, steam on high for 10'
Add amanatto, and remaining mixture
The book sais to steam for another 20'; Miya prefers hers tougher, so she steams for longer.
➡️ Revising this recipe in III 26, I think it might be better to make a more classical 外郎 dough, and to make the amanatto with a mix of different coloured beans!