Beef shepherd's pie is a savory gluten-free casserole. Seasoned ground beef and vegetables are topped with mashed potatoes and baked in the oven. Warm and comforting, this flavorful dish is a family favorite.
Preheat the oven to 375 F.
Peel and quarter the potatoes. Place in a large pot and cover with cold water. Add a tsp of salt. Bring the water to boil. Turn the heat down to medium, cover and cook the potatoes until a fork gently glides into the potatoes (about 10 - 12 minutes). Turn off the heat. Carefully, drain the hot water. Return potatoes to the pot. Add the sour cream, milk, butter. Use a potato masher to mash up the potatoes until they are fluffy. Season with remaining salt and pepper. Adjust seasoning to taste. Cover to keep warm.
Use a large skillet. Heat the olive oil and 2 tablespoons butter over medium-high heat. Add the onion, carrots and celery and saute for several minutes until the vegetables begin to go tender. Add the minced garlic.
Push the vegetables to the side and add the ground beef. Use a wooden spoon to break up the beef. Add the oregano, salt and pepper. Once the beef has started to brown, push aside a small opening. Add the tomato paste to this area and cook for a minute or two. Stir all vegetables and beef together. Add the Worcestershire sauce and beef broth.. Simmer for several minutes until the beef is nicely browned. Finally, stir in the peas.
Transfer the filling and evenly distribute to a 2-quart oval casserole dish. Top the beef filling with the mashed potatoes and spread them out. Use a fork to fluff up the potatoes creating a decorative pattern on top. Dot the potatoes with the remaining tablespoon of butter.
Bake in the oven for 35 - 40 minutes. The potatoes should be lightly browned and the juices will bubble around the edges. Allow the sheperd's pie to cool for 10 minutes prior to serving.