Place the biggest wok you can find on your outdoor grill burner, preferably one where you can keep the heat at a medium level. Or you could do this indoors on the stove.
Add one stick of butter, and as it begins to melt, add the chopped onion.
While stirring, add the Oyster Sauce, and then add the sugar.
Once the butter has melted and the onions are translucent, add the whole crabs to the wok.
Then crack black pepper over the top of them.
Using a big utensil like a wok shovel or wire skimmer, move the crabs around the wok so that every side and claw is exposed to the heat.
Continue scooping the onion-butter sauce over the crabs.
If the onions start to brown too quickly, turn the heat down a little, to keep them from burning. The onions will caramelize and eventually stick to the crabs, creating the finger-licking goodness.
Dump the crabs and sauce into a big serving pan or platter, making sure to scrape all the sauce and caramelized onions into the pan.
Use French Bread to sop up the remaining sauce and onions from bottom of the serving pan.
Notes
* To clean the crabs for this recipe, scrub the whole crab clean with a little brush, especially the claws. Then, remove the shell and dispose. Lastly remove the private parts, filters and other junk you don't eat on a boiled crab. Place cleaned crabs in a pan to await the wok.