How to Make It
Preheat the oven to 250°. Spread the bread rounds on a large baking sheet and bake for about 25 minutes, turning once, until dry but not browned. Let cool completely.
Meanwhile, set up a large ice bath. In a large pot of boiling water, cook the lobster until bright red but not cooked through, about 2 minutes. Transfer the lobster to the ice bath to cool completely.
Twist the lobster bodies from the tails. Using scissors, cut along the underside of the shells and remove the meat. Halve the tails lengthwise and discard the dark intestines. Crack the claws and remove the meat in one piece. Remove the knuckle meat. Cut the lobster meat into chunks.
In a food processor, pulse the pork with the water chestnuts, scallions, ginger and garlic until finely chopped. Add the lobster, sake, chile-bean paste, soy sauce, salt, egg and cornstarch and puree until a paste forms.
In a large saucepan, heat 1 1/2 inches of peanut oil to 325°. Spread 2 teaspoons of the lobster paste on each round of bread. In batches, add the toasts paste-side down to the hot oil and fry, turning once, until browned and crisp, about 4 minutes total. Using a slotted spoon, transfer the lobster toasts to a paper towel-lined baking sheet to drain. Serve right away with chile sauce, soy sauce and hot mustard.