In a large skillet over medium-high heat, cook the ground beef until no longer pink. Add the onion and garlic and cook for an additional 2 minutes.
Stir in the frozen vegetables, Worcestershire sauce, thyme, parsley, salt, and pepper. Cook for an additional 5 minutes, or until vegetables are cooked through.
Transfer the mixture to a 9x13 inch baking dish. Top with the mashed potatoes and spread evenly.
Sprinkle the top with the cheddar cheese.
Bake in preheated oven for 25 minutes, or until the edges are bubbling and the cheese is melted.
Interesting Facts
Shepherd's Pie is a traditional British dish, but has recently become popular in the United States.
The dish is traditionally made with mashed potatoes, but can also be made with mashed sweet potatoes or squash.
Shepherd's Pie is a great way to use up leftover mashed potatoes.