Preheat your oven to 400°F (200°C). In a mixing bowl, combine ground beef, breadcrumbs, egg, onion, garlic, Worcestershire sauce, salt, black pepper, and thyme. Mix gently until just combined.

Shape the mixture into 1-inch meatballs and place on a parchment-lined baking sheet. Bake for about 20 minutes or until cooked through.

Heat olive oil in a skillet over medium heat. Sauté diced onion and minced garlic for 3-5 minutes until translucent.

Pour in beef broth and a splash of Worcestershire sauce. Bring to a simmer and cook for about 5 minutes.

Mix cornstarch with cold water to create a slurry and whisk into the gravy, simmer for another 2-3 minutes until thickened.

Boil peeled and chopped potatoes in salted water for 15-18 minutes until fork-tender. Drain and return to pot.

Mash the potatoes with milk, butter, salt, and pepper. Stir in fresh parsley.

Transfer baked meatballs to the skillet with gravy and coat well. Let them simmer for a minute.

Serve by placing a scoop of mashed potatoes on a plate, top with meatballs, and drizzle with gravy.