Preheat your oven to 200°C. Grease a baking dish.

In a large skillet, cook the ground beef over medium heat until browned. Drain excess fat.

Add the chopped onion and minced garlic to the skillet. Cook until the onion is soft and translucent.

Stir in the frozen peas and carrots, beef broth, tomato paste, Worcestershire sauce, dried thyme, salt, and pepper. Simmer for 5-7 minutes, until the mixture thickens.

Transfer the beef mixture to the prepared baking dish. Spread the mashed potatoes evenly over the top.

If using, sprinkle shredded cheddar cheese over the mashed potatoes.

Bake in the preheated oven for 20-25 minutes, or until the top is golden and the filling is bubbling.

Let cool for a few minutes before serving.