Creating Savoury Breakfast Strata is straightforward if you follow these streamlined steps:

1. Prepare the Bread: Cut the day-old bread into cubes, about 1-inch in size. Place them in a large mixing bowl.
2. Whisk Eggs and Milk: In a separate bowl, whisk together the eggs, milk, mustard, salt, and pepper until well combined.
3. Mix Ingredients: Pour the egg mixture over the bread cubes and stir gently until the bread is well-coated. Allow it to soak for 10 minutes.
4. Add Fillings: Gently fold in the shredded cheese, diced vegetables, and cooked sausage or ham if using.
5. Transfer to Baking Dish: Grease a 9×13-inch baking dish. Pour the mixture into the dish, spreading it evenly.
6. Cover and Refrigerate (optional): If preparing ahead of time, cover with plastic wrap and refrigerate overnight. If baking immediately, skip this step.
7. Preheat Oven: Preheat your oven to 350°F (175°C).
8. Bake: Remove the plastic wrap (if used) and bake for 45-50 minutes, or until the strata is puffed and golden brown.
9. Cool and Serve: Once baked, allow it to cool for 5-10 minutes before slicing. Garnish with fresh herbs if desired.

These steps ensure that you create a perfect Savoury Breakfast Strata every time, resulting in a dish that is hearty and full of flavor.