Start by cleaning the mud or Dungeness crabs under cold running water to eliminate any impurities. Using a mallet, carefully crack the legs and claws.

In a blender, combine chopped onions, garlic cloves, ginger, and dried chillies. Blend until you achieve a coarse puree.

Heat a large wok over medium-high heat and add the peanut oil. Once hot, add the prepared spice paste and sauté for 3-4 minutes.

Stir in salt and sugar, then carefully add the crabs to the wok. Pour in the chicken stock and cover the wok, cooking for 5-6 minutes.

Remove the lid and stir in the red chilli sauce, soy sauce, and tomato ketchup. Return the crab shells to the wok and let it simmer.

Create a slurry with the cornstarch and a splash of water. Slowly pour this into the wok while stirring continuously.

Finally, stir in freshly chopped coriander leaves and remove the wok from heat. Serve hot, alongside steamed mantou or rice.