Preheat the oven to 375 degrees. In a large skillet, heat the oil over medium-high heat for 1 minute. Add the onion and stir-fry until tender. Stir in ground beef, then add carrot, parsley, garlic and thyme. Cook until beef is thoroughly browned, stirring frequently. Drain off any excess oil. Add soy sauce and stir well. Taste, and add more salt and pepper if desired. Spread the meat mixture evenly in the bottom of a deep pie dish. top with green beans, then with mashed potatoes. Bake in preheated oven for 30 minutes.