Sprinkle 2.5 cups of the oyster crackers over the bottom of greased 13 x 9 x 5 cm baking dish.Layer onions,water chestnuts,peas and crabmeat crackers.Top with remaining crackers.Blend together remaining ingredients and pour over layers.Cover and refrigerate several hours or overnight. Bake in preheated 350 degree oven until golden brown,30 to 35 minutes. Cut into squares to serve.Garnish with tomatoes and green onions,if desired.Makes 8 servings. * Please Note: To keep down cost,use 1 cm slices of new imitation crabmeat sticks,termed "Surimi" in place of crabmeat. ----