In a large saucepan over medium high heat, saute carrots and onions in 1 Tbsp olive oil about 5 minutes. Add garlic and saute for another minute. Add a pinch of salt and pepper.
Transfer to large stock pot and add beef broth, lentils, barley, thyme and soy sauce. Bring to a boil; reduce heat and simmer until lentils are tender, about 30 minutes. Stir in corn, green peas and tomatoes; continue simmering another 10 minutes.
While lentils are simmering, brown ground beef, and cook potatoes. Place potatoes in large stockpot; add enough water to cover. Bring to a boil. Reduce heat to medium-low; cover loosely and boil gently for 15 to 20 minutes or until potatoes are tender. Drain well. Mash. Season with butter, salt and pepper to taste. Cover and keep warm.
Preheat oven to 350 degrees.
Add ground beef to beef stock mixture.
Lightly grease a 3 quart baking dish and pour lentil mixture into dish. Use a spatula to spread the mashed potatoes over the top of the ground beef/lentil mixture. Sprinkle with a pinch of salt and pepper.
Bake 30 minutes, or until potatoes are lightly browned on top. Let stand about 15 minutes before serving.
To make a vegetarian shepherd's pie recipe, omit the ground beef and use vegetable broth in place of beef broth.