Castella

Castella was brought to Japan through the Nanban trade during the Sengoku period, arriving in Nagasaki with Portuguese missionaries and merchants. Wikipedia documents that it has existed in Japan for more than four hundred years, and after adaptation to Japanese tastes is classified as wagashi. The Japanese additions — mizuame (starch syrup) for moisture retention and coarse zarame sugar at the bottom — distinguish it from the Portuguese original.

A slice of castella is pale gold, dense and moist, with a fine, even crumb and a slightly sticky surface. The bottom carries a layer of coarser sugar for crunch. The flavor is pure egg and sugar — rich but not heavy — with a faint honeyed sweetness from the starch syrup. Eaten in thin slices with tea.

Castella rests on a whole-egg sponge with added starch syrup. Eggs and sugar are whipped to the ribbon stage, incorporating air; sifted flour is folded in gently. The starch syrup (mizuame) — a glucose-based syrup — is the Japanese innovation: it acts as a humectant, binding water and preventing the cake from drying out, which gives castella its characteristically dense, moist texture that keeps for days. The batter is baked slowly in a wooden frame lined with paper; the slow bake sets the crumb evenly without a tough crust. The coarse zarame sugar at the bottom sinks during baking and creates the textural contrast.