1. Wash the callaloo greens (or spinach or chard) under cold running water and discard any discolored leaves. Leave the callaloo greens whole but, if you are using spinach or chard, bunch the leaves together and shred them into fine strips.
2. In a heavy 4- to 5-quart casserole, melt the butter over moderate heat. Add the onions and garlic and, stirring frequently, cook for 5 minutes, until they are soft and transparent but not brown.
3. Add the greens and turn them about with a spoon for 4 or 5 minutes, until they glisten with butter and become somewhat limp.
4. Stir in the stock, coconut milk, salt and a few grindings of pepper. Bring to a boil over high heat, reduce the heat to low, and simmer uncovered for about 10 minutes, or until the greens are tender.
5. Add the crab meat and "A-1" or "Pickapeppa", and stir for 2 or 3 minutes to heat the crab through.
6. Taste for seasoning and serve at once, from a heated tureen or in individual soup plates.
