Irish Shepherd's Pie

Instructions

1. Prepare the potatoes
   Place the potatoes in a large pot and cover with cold water. Add 1 teaspoon salt and bring to a boil. Reduce heat and simmer until potatoes are fork-tender, about 20 minutes. Drain well and return to the pot.
2. Make the mashed potatoes
   Add the warm milk and butter to the potatoes. Mash until smooth and creamy. Season with salt and pepper to taste. Cover and set aside while preparing the filling.
3. Cook the meat mixture
   Heat olive oil in a large skillet over medium heat. Add the onions, carrots, and celery, cooking until softened, about 6-8 minutes. Add the garlic and cook for another minute until fragrant.
4. Brown the lamb
   Add the ground lamb to the vegetables, breaking it up with a wooden spoon. Cook until browned and no longer pink, about 8-10 minutes. Drain excess fat if necessary.
5. Finish the filling
   Stir in the tomato paste and cook for 2 minutes. Add the beef stock, Worcestershire sauce, and thyme. Simmer uncovered for 10-15 minutes until the liquid has reduced and the mixture has thickened. Stir in the frozen peas and season with salt and pepper to taste.
6. Assemble the pie
   Preheat oven to 375°F (190°C). Transfer the meat mixture to a 9x13 inch baking dish, spreading it evenly. Carefully spoon the mashed potatoes over the top, then use a fork to create ridges on the surface, which will crisp up during baking.
7. Bake the shepherd's pie
   Dot the top with small pieces of additional butter if desired. Bake in the preheated oven for 35-40 minutes, until the top is golden brown and the filling is bubbling around the edges.
8. Rest and serve
   Remove from the oven and let stand for 10 minutes before serving. Garnish with fresh thyme leaves if desired and serve hot.