Creating Breakfast Strata with Croissants is simple when you follow these easy steps:

1. Prepare the Dish: Preheat your oven to 350°F (175°C). Grease a 9×13-inch baking dish with butter or cooking spray.
2. Assemble Croissants: Place the cut croissant pieces evenly in the greased baking dish.
3. Add Cheese and Meat: Sprinkle the shredded cheese and diced ham or sausage (if using) over the croissant pieces.
4. Add Vegetables: Distribute the chopped vegetables evenly across the dish.
5. Mix the Custard: In a large mixing bowl, whisk together the eggs, milk, Dijon mustard, salt, black pepper, and thyme until fully combined.
6. Combine Mixtures: Pour the egg mixture evenly over the croissant and filling layers in the baking dish. Press down gently to ensure all pieces are soaked.
7. Rest: Cover the dish with plastic wrap and let it rest in the refrigerator for at least 30 minutes, or overnight for maximum flavor absorption.
8. Bake: Remove the plastic wrap and bake in the preheated oven for 45 minutes, or until the top is golden brown and a toothpick comes out clean.
9. Cool Slightly: Let the strata cool for about 10 minutes before serving.
10. Garnish: Sprinkle with fresh parsley for a burst of color and flavor right before serving.

Following these steps will lead you to create an amazing Breakfast Strata with Croissants that everyone will rave about!