Rempah is a Malay word used to describe the spice pastes used in many dishes throughout the Southeast Asian region.Depending on the recipe, various ingredients are pounded together in a mortar and pestle, then fried slowly in oil until intensely fragrant.he resulting paste is then used as a recipe base for various curries and stir-fries. Aromatic and piquant, the flavour of homemade rempah is far superior to the ready-made curry pastes and stir-fry sauces found in supermarkets.