Mashed potatoes: Make the mashed potatoes per the recipe instructions (links to my fluffy mashed potatoes recipe). Preheat the oven to 400 degrees F.
In a 10 or 12 inch oven-proof skillet, cook the ground beef over medium-high heat, breaking it apart, until browned and cooked through. Drain excess fat. Transfer the cooked beef to a plate and set aside.
Reduce to medium heat. To the same skillet, add a few drizzles of olive oil and cook the diced onions until softened, about 4 minutes. Add the minced garlic, thyme, rosemary, and paprika, and cook for another 1 to 2 minutes until fragrant.
Return the cooked beef to the skillet. Stir in the tomato paste, Worcestershire sauce, and canned diced tomatoes until combined.
Sprinkle the flour over the mixture and stir to evenly coat. Gradually, add the beef broth, braking up any lumps. Bring to a simmer (it will thicken). If too thick, add more broth as needed.
Stir in the mixed vegetables and simmer on low for 3-4 minutes. Season with salt and pepper. Turn off the heat.
Evenly spread the mashed potatoes over the filling. Brush with melted butter. Decorate by creating patterns with a rubber spatula or fork. Note: if the mashed potatoes are cold, reheat before using so it's easier to spread.
Place the skillet on a large sheet pan in case some of the filling spills over. Bake for about 25 minutes until golden brown. If you want it more golden brown, broil for about 1-2 minutes. Garnish with chopped parsley. Enjoy!