Indonesian cooking is built on two foundational preparations: bumbu (spice paste) and sambal (chilli-based condiment/sauce). There are hundreds of regional sambals and bumbus across the 17,000-island archipelago. Bumbu is the flavour base cooked into dishes (similar to Malaysian rempah). Sambal is served alongside as a condiment but can also be cooked into dishes. Both are built through pounding and frying, and the specific combination defines the regional cuisine — Balinese, Javanese, Sumatran, Padang, each has distinct signatures.
Bumbu typically includes shallots, garlic, chillies, galangal, ginger, turmeric, lemongrass, candlenuts, and shrimp paste (terasi/trassi). Pounded in a cobek (stone mortar) and fried until fragrant and oil separates. Sambal oelek is the simplest: raw chillies pounded with salt. Sambal matah (Balinese): raw shallots, lemongrass, chilli, and lime — never cooked. Sambal goreng: fried sambal with tomato and shrimp paste. Sambal terasi: the most common, chillies with toasted shrimp paste. The terasi MUST be toasted before use — raw terasi tastes overwhelmingly fishy.
Toast terasi wrapped in foil over an open flame for 30 seconds per side — the smell will fill the kitchen but the flavour transformation is essential. For rendang (Indonesia's, not Malaysia's): the bumbu is fried, coconut milk added, then simmered for 3-4 hours until completely dry — it's not a curry, it's a dry-fried preparation. The kerisik (toasted coconut paste) added near the end is what gives Sumatran rendang its unique nutty depth. Every Indonesian meal is built around rice, sambal, and a protein — the sambal is not optional.
Not toasting terasi — it transforms from pungent to savoury when exposed to dry heat. Using a blender for bumbu when the recipe calls for pounding — different texture. Not frying bumbu long enough — as with Malaysian rempah, the oil must separate. Treating all sambals as interchangeable — each has a specific purpose and flavour. Under-estimating Indonesian chilli heat.