To kill the crab, either plunge it into a large pot of boiling water for a minute, or place it on its back on a cutting board and split the body down the middle with one quick cut with a heavy knife. Use the first method if you wish to use the upper shell in presenting your dish. Holding the crab body by the legs, pull off the shell. Discard the feathery gills on both sides of the body and the spongy mass in the middle of the back; rinse until nothing but shell and meat show. Pull out the bits of greenish fat from the corners of the shell. Rinse both the body and shell and drain thoroughly.

Split the body of the crab (if it is not already split) into 2 halves with each cluster consisting of a set of 3 legs and a claw. Carefully crack each leg and claw segment with a mallet. Place the clusters in a large bowl with the oil, ginger, garlic, chilies and a generous grinding of pepper. Marinate for 1 to 4 hours in the refrigerator. You may need to break your clusters into individual leg and claw sections to be able to submerse the legs while marinating. Remove crab from marinade 15 minutes before cooking.

Grilling:

Grill the halves and the shell over a hot fire until outer shells are bright red and meat in the largest sections is opaque, about 3 to 4 minutes per side.

Roasting:

Place crab halves and shell in a roasting pan lightly oiled with a bit of the marinade and roast in a 450F, about 12 to 15 minutes.

Dipping Sauce:

Strain vegetables out of marinade and combine with the butter in a saucepan. Simmer for 5 minutes and season to taste. Serve in small bowls as a dipping sauce for the crab.