Add oil to a large skillet and place it over medium-high heat for 2 minutes.
Add onions and cook for 5 minutes, stirring occasionally.
Add ground beef (or ground lamb) to the skillet, breaking it apart with a wooden spoon.
Add parsley, rosemary, thyme, salt, and pepper. Stir well. Cook for 6-8 minutes until the meat is browned, stirring occasionally.
Add Worcestershire sauce and garlic. Stir to combine. Cook for 1 minute.
Add flour and tomato paste. Stir until well incorporated and no clumps of tomato paste remain.
Add 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.