Blitz the paste together in a food processor or pound in a pestle and mortar until smooth. Mix the sauce ingredients together in a bowl.
From the dressed crab shell, separate out the white meat from the brown meat. Keep the shell to add to the sauce later.
Butterfly the prawns using scissors, keeping the shell and head on. Devein the prawns, then score their flesh 4-5 times horizontally to allow them to butterfly easily when cooking.
In a large thick-based wok or pan over a medium heat, heat 2-3 tbsp vegetable oil. Add the paste and fry for 8-10 mins, stirring occasionally, until fragrant and aromatic and the liquid has reduced.
Now pour in the sauce and stir through to combine with the cooked paste.
Once the sauce is vigorously boiling, add the chicken stock. Add the brown crab meat into the sauce, together with the empty crab shell. Turn the heat up high and bring to a boil. Once boiling, turn the heat down to medium-low and simmer for 30 mins.
Just before finishing, turn the heat up to a medium heat, then place the butterflied prawns into the stock to boil for 4-5 mins, depending on their size. This should reduce the sauce to a silky, syrupy consistency.
Add the white crab meat into the sauce for the last minute.
Remove the sauce from the heat. Plate up the prawns and remove the crab shell. Then, just before serving, pour the beaten egg into the hot sauce in one go.
Give it one gentle stir then pour the sauce with its fresh whisps of ‘eggy-ness’ over the prawns to finish.
Garnish with fresh coriander and serve with fried bao.