Bolu kukus (steamed sponge cake) is the everyday steamed cake of Indonesian home and market baking — simple in concept (steam a batter of rice flour, egg, sugar, and coconut milk), but with a specific quality indicator that has become its defining visual: the natural bloom (mekar) of the cake's surface during steaming. A properly made bolu kukus opens at the top, the steam forcing the surface to crack and flower into a 3–4 petal pattern as the interior expands. This bloom is a sign of correct batter consistency, correct steam intensity, and correct tin filling level. No bloom (or a flush, uncracked surface) indicates incorrect batter or insufficient heat. The bloom is not merely aesthetic — it is the diagnostic.
Bolu Kukus — Steamed Rice Flour Cake that Blooms
Indonesian Deep Extraction — Batch 14