Follow these simple steps to create your Easy Shepherd’s Pie Casserole:

1. Preheat Oven: Preheat your oven to 400°F (200°C).

2. Cook the Meat: In a large skillet over medium heat, brown the ground lamb or beef until fully cooked. Drain excess fat if necessary.

3. Add Aromatics: Stir in the diced onion and minced garlic. Cook until the onion is translucent.

4. Incorporate Vegetables: Add the mixed vegetables to the skillet and continue cooking for about 3-5 minutes.

5. Mix in Broth: Pour in the beef or vegetable broth and Worcestershire sauce. Bring to a simmer.

6. Season: Sprinkle in dried thyme and season with salt and pepper. Allow the mixture to simmer until slightly thickened, about 5 minutes.

7. Layer the Casserole: Spread the meat and vegetable mixture evenly in a baking dish. Top it with the mashed potatoes, smoothing them out with a spatula.

8. Add Cheese: If using, sprinkle shredded cheddar cheese over the mashed potatoes.

9. Bake: Place the casserole in the preheated oven and bake for 30-35 minutes or until the top is golden and bubbling.

10. Cool Slightly: Remove from the oven and let it cool for a few minutes before serving.

These straightforward instructions make it easy for anyone to create this delicious dish seamlessly.