Heat olive oil in a large skillet over medium-high heat. Add the chopped onion and cook for about 5 minutes until softened and slightly browned.
Add the ground beef or lamb to the skillet. Break the meat up with a wooden spoon while sprinkling in the dried herbs, salt, and pepper. Cook until the meat is browned and fully cooked through.
Stir in the minced garlic and Worcestershire sauce. Next, mix in the flour and tomato paste. Slowly pour in the beef broth while stirring to create a thick mixture.
Add the frozen peas, carrots, and corn to the skillet. Simmer for about 5 minutes until heated through.
Potato Preparation
Preheat the oven to 400 degrees Fahrenheit. Boil the cubed potatoes in salted water for 10–15 minutes until fork-tender.
Drain the potatoes and mash them with the butter, half and half, garlic powder, salt, pepper, and parmesan cheese until smooth.
Assembly and Baking
Spoon the meat filling into a baking dish. Top with the creamy mashed potatoes, spreading them evenly.
Bake in the preheated oven for 25-30 minutes until the top is golden and slightly crispy.
Let the Shepherd's Pie rest for 10-15 minutes before serving.
Notes
Use fresh herbs for better flavor.
Be careful not to over-mash the potatoes for a fluffy texture.
Make ahead by preparing contents separately, then assemble before baking.