Preheat the oven to 375°F. Grease an 11x7-inch (2 quart) glass baking dish with cooking spray. Set aside.
Cook mashed potatoes according to package instructions. Set aside.
24 ounces refrigerated mashed potatoes
In a large skillet, heat oil over medium-high heat. Sauté the onion in the oil for about 5-7 minutes occasionally stirring until it becomes soft.
1 teaspoon olive oil, 1 yellow onion
Add the beef and cook for 5 to 7 minutes, stirring occasionally, until it's completely cooked. Drain any excess fat.
1 ½ pounds lean ground beef
In a small bowl, whisk together the broth and flour. Add broth mixture to the beef mixture and bring to a boil. Cook for 3 minutes, stirring constantly, until it thickens.
2 cups beef broth, 1 Tablespoon all-purpose flour
Add the mixed vegetables, tomato paste, Worcestershire sauce, salt, and pepper into the skillet. Cook over medium heat for 5 minutes, stirring frequently, until the vegetables are heated through.
3 cups frozen mixed vegetables, 1 Tablespoon tomato paste, 1 teaspoon Worcestershire sauce, 1 teaspoon salt, ½ teaspoon black pepper
Transfer beef mixture to the prepared baking dish and spread mashed potatoes over the top.
Bake for 20 minutes or until golden brown.
Garnish with fresh chopped parsley before serving
fresh chopped parsley