Preheat the Oven:
Set your oven to 375°F (190°C). Lightly grease a 9x13-inch casserole dish.
Prepare the Meat Mixture:
In a mixing bowl, combine the ground beef, chopped onion, garlic powder, onion powder, smoked paprika, salt, and pepper. Mix until well combined.
Cook the Meat (Optional):
If desired, sauté the meat mixture in a skillet over medium heat until browned. This step ensures even cooking and reduces grease in the casserole.
Layer the Meat:
Spread the ground beef mixture evenly in the bottom of the casserole dish. If adding peas or carrots, layer them on top of the meat.
Prepare the Mashed Potatoes:
If using store-bought mashed potatoes, heat them slightly and mix in a splash of milk for creaminess. Spread the mashed potatoes evenly over the meat layer.
Add the Cheese:
Sprinkle the shredded cheddar cheese over the mashed potatoes.
Top It Off:
Drizzle ketchup over the top, creating a lattice design or simply spreading it lightly.
Bake:
Bake the casserole in the preheated oven for 25–30 minutes, or until the cheese is melted and bubbly.
Serve:
Let the casserole cool for 5 minutes before slicing. Garnish with parsley if desired.