Japan-wide — Heian court tradition dating to 9th century
Tsukimi (moon viewing) is the mid-autumn harvest celebration held on the 15th day of the 8th lunar month, coinciding with the harvest full moon. The food culture of tsukimi centres on round, white foods representing the full moon — particularly tsukimi dango (round white rice dumplings stacked in pyramids), satoimo (taro root), chestnuts, and edamame offered to the moon on a bamboo grass decoration. In modern Japan, tsukimi has a second, commercial expression through seasonal food products — most famously tsukimi burger (McDonald's Japan seasonal offering with egg representing the moon), tsukimi soba and udon (topped with a raw or poached egg whose yolk represents the moon), and tsukimi sake. The aesthetic is central to Japanese food culture's integration of seasonal ritual with flavour — the visual act of eating round white foods under the autumn moon is as important as taste.
Mild, starchy, comforting — taro and dango are vehicles for subtle seasonings; the aesthetic experience transcends pure flavour
Round, white, or yellow foods symbolically reference the full moon; taro (satoimo) is the essential harvest offering — boiled or steamed; dango are shaped round and white and served in groups of 15 to represent the lunar calendar; the 'harvest moon egg' tradition: cracking a raw egg yolk onto noodles represents the moon's reflection in water.
Satoimo no nikkorogashi (simmered small taro in dashi and soy) is the definitive tsukimi vegetable dish; white dango dusted with black sesame or coated in sweet miso represent moon and shadow; the 'tsukimi egg' technique in noodle soups: slide raw egg yolk onto the surface of hot soup just before serving — it sets partially from the heat into a moon-like roundness.
Treating tsukimi purely as a children's activity rather than a serious aesthetic and cultural practice; using dango shapes other than round (triangular or elongated dango break the symbolism); ignoring the distinction between the 15th lunar moon (Jyuugoya) and the 13th moon (Jyuusanya) — both have associated food customs.
Japanese Food Culture — Naomichi Ishige