Prep the crab: Gently crack the claws of the cleaned brab without removing any shell. Springle the crab with tapioca flour to coat.
Fry the crab: On medium-high heat, heat a wok until smoking hot and pu in 1/4 cup of the groundnut oil. When the oil is hot, fry the crab until it turns red, about 3 minutes. Remove the crab and set aside.
Make the salted egg sauce: Turn down the heat to medium and discard all but 2 tbsp of the oil. Fry the minced garlic and curry leaves until fragrant. Lower the heat and add the butter and mashed salted egg yolks. Stir constantly to create a frothy foam. Stir in the evaporated milk, sugar and salt.
Ticken the sauce: The tapioca coating on the crab and evaporation will ticken the salted egg yolk sauce as it cooks. Continue to stir until you reach the consistency of cream. Add a little warm water if it is too thick. Taste and adjust seasoning.
Crab toss, garnish and serve: Return the crab to the wok and toss for a few seconds until all the crab is well coated with the salted egg yolk sauce. Dish the crab out to a serving platter lined with iceberg lettuce leaves. Garnish with coriander leaves and serve immediately.