In a medium bowl, combine diced chicken, soy sauce, vinegar, sesame oil, chili paste with garlic, 1 Tbsp dry mustard, scallions, red pepper and water chestnuts.
Mix well and set aside.
Turn half the bread cubes in buttered 11 x 7 baking dish. Sprinkle with half the cheese.
Distribute half the chicken mixture over cheese. Cover with remaining bread cubes and remaining 3/4 Tbsp dry mustard until blended.
Pour evenly over casserole. Cover with plastic wrap. Refrigerate several hours, or overnight.
Preheat oven to 350° F. Bake, uncovered 40 to 45 minutes, until top is golden and center is set. Let cool 5 minutes, then cut into squares or rectangles to serve.
Servings: 6