Spread ground beef in a 20 cm x 20 cm x 5 cm baking dish. Sprinkle with salt. Bake in 180ºC oven for 15 minutes. Drain. Mix eggs, mustard, garlic, milk and flour. Pour over hot beef. Sprinkle the shredded cheese over all. Cover the top evenly with toasted bread squares. Bake until cheese custard is set, 30 to 35 minutes. Serves 6.