Pre-heat the oven to 400 °F. Lightly spray a pie dish with nonstick spray.
Wash, peel and chop the potatoes. Put the potatoes in a medium saucepan and fill the saucepan with just enough water to cover the potatoes.
Put the lid on the saucepan and bring the water to a boil over medium-high heat. When the water boils, remove the lid and let the potatoes boil for about 20 minutes, until easily pierced with a fork.
Drain the potatoes and return them to the saucepan along with 1 ounce of cheddar cheese and 1 tablespoon of margarine. Mash it all together with a potato masher.
Add ½ cup milk, ¼ teaspoon pepper, and a pinch of salt. Set aside.
Meanwhile, while you're waiting for the potatoes to boil, start making the filling by heating 1 teaspoon of oil in a skillet over medium heat.
Add the carrot to the hot pan and cook about 3 to 5 minutes, until the carrot is soft.
Add the garlic and cook for 1 more minute.
Add the ground beef and cook, stirring frequently, until the beef is no longer pink at all.
Sprinkle the beef with 1 tablespoon all-purpose flour and cook for 1 minute more.
Stir in the tomato paste
Stir in the beef broth, the thawed pearl onions, dried rosemary, dried thyme, and Worcestershire sauce.
Bring the mixture to a boil. When the mixture boils, turn the heat down to "medium-low" and let it simmer for about 15 minutes.
Stir the thawed peas into the filling.
Spoon the filling into the prepared pie dish and spread it around in an even layer.
Spoon the potatoes on top of the filling and use the back of a spoon or a spatula to spread the potatoes in an even layer.
Put the pie dish in the oven and bake at 400 °F for about 25 minutes, until the potatoes are slightly browned on top.