Using sharp kitchen shears, snip off the eyes/mouth of the crabs, scooping out the goop behind the eyes.Tear or cut off the dead man's fingers (gills) on the underside of the crab. Tear or cut off the apron (triangular flap) as well.
In a large dutch oven with a heavy bottom, heat the peanut oil. Add the garlic, ginger, and Thai bird chile. Stir for about a minute, or until fragrant.
Add the mashed black beans and stir for another 30 seconds. Add the crabs and continue to stir until the crab changes color, about a minute. Remove the crabs to a plate and hold.
Add the Xiao Xing, tomato sauce, chili sauce, sugar, and a pinch of ground pepper and salt to taste. Bring to a boil, then reduce to a simmer.
Add the crabs back in and simmer until cooked through, about another minute.
Make a slurry with the water and cornstarch and add to the pot, stirring until thickened. Add the eggs and continue to stir until cooked, about 30 seconds. Stir in the cilantro.
Serve one crab per person with sauce spooned over the top. Slice or tear a good chunk of crusty bread and set on the side for mopping up sauce.