Prep the base: Roughly chop the large and small chilies, shallots, garlic, and tomatoes.
Sauté aromatics: Gently sauté the garlic until translucent and fragrant.
Build the heat: Add the shallots and chilies. Cook until soft and deeply aromatic.
Add depth: Stir in shrimp paste and tomatoes. Cook until the tomatoes break down and the paste is fully incorporated.
Blend to perfection: Remove the mix from the pot and blitz until smooth.
Finish with flavour: Return the paste to the pot. Add palm sugar, oyster sauce, salt, pepper, and castor sugar.
Cook it out: Simmer until the paste turns a rich red and is intensely fragrant — about 10 minutes.
