Brown sausage in a skillet, breaking into small pieces as it cooks. Drain and let cool. In a large bowl, whisk together eggs, milk, mustard, salt and pepper (if using). Add sausage, cheese and bread to the egg mixture, mixing gently with a large spoon. Carefully transfer to a 3 quart baking dish, cover and refrigerate overnight. Uncover and place dish in the oven and heat oven to 350 degrees. Allow soufflé to bake for about 60 minutes or until puffed and golden. Serve hot and enjoy!