Part 2:
Make the Meat Filling:
Add the oil to a large skillet and place it over medium-high heat for 2 minutes. Add the onions. Cook 5 minutes, stirring occasionally.

Add the ground beef (or ground lamb) to the skillet and break it apart with a wooden spoon. Add the parsley, rosemary, thyme, salt, and and pepper. Stir well. Cook for 6-8 minutes, until the meat is browned, stirring occasionally.

Add the Worcestershire sauce and garlic. Stir to combine. Cook for 1 minute.

Add the tomato paste. Stir until well incorporated and no clumps of tomato paste remain.

Add the broth, frozen peas and carrots, and frozen corn. Bring the liquid to a boil then reduce to simmer. Simmer for 5 minutes, stirring occasionally.

Set the meat mixture aside. Preheat oven to 400 degrees F.

Final Step:
Assemble the casserole.
Pour the meat mixture into a 9x9 (or 7x11) inch baking dish. Spread it out into an even layer. Spoon the mashed potatoes on top of the meat. Carefully spread into an even layer.
If the baking dish looks very full, place it on a rimmed baking sheet so that the filling doesn’t bubble over into your oven. Bake uncovered for 25-30 minutes.

Lily isn't vegetarian, so use the lactose free potatoes with the meat filling.