It's called 羊羹, but actually is こなし. It's very 詫び, but in that regard, very pretty.
Soak 竹の皮 for 2 hours in water.
Mix 100 gr こし餡 with 15 gr flour (I tried 11.4. half buckwheat and white, and that was much nicer), then carefully add 2 (or a lot more) chopped boiled chestnuts. (Last time I used cognac-chestnuts, which was nice; but I think just plain chestnuts are also fine ⸺ the frozen ones from Migros work perfectly fine).
Pinch of salt.
Up to 5 ml water to adjust consistency of あん (or good cognac, which is very nice)
Wrap in the dried bamboo skin, use some strips from the edge to tie up and steam on high for 30'.
It's nicer the day after.