Peel and chop about 2 pounds of potatoes into even chunks, then place them in a large pot. Cover with cold water, add a pinch of salt, and bring to a boil over medium-high heat. Cook until tender, about 15–20 minutes. Drain the potatoes and return them to the pot, mashing with 4 tablespoons of butter and ½ cup of milk until creamy and smooth. Set aside to cool slightly.

In a large skillet over medium heat, add a drizzle of oil and sauté one finely chopped onion until translucent, about 5 minutes. Next, add 1 pound of ground meat (beef or lamb) and cook, breaking it apart, until browned, roughly 7–8 minutes. Stir in diced carrots, frozen peas, and 1 cup of beef broth, allowing it to simmer for an additional 5 minutes until heated through and the carrots are tender.

Preheat your oven to 400°F (200°C). In a large baking dish, spread the savory meat filling evenly across the bottom. Gently spoon the creamy mashed potatoes over the meat, smoothing them into an even layer with a spatula. Use a fork to create texture on the top for a crispy finish.

Place the assembled Shepherd’s Pie in the preheated oven and bake for 20–25 minutes. You’ll know it's ready when the top is golden brown and slightly crispy. Keep an eye on the pie after 20 minutes to prevent over-browning. Remove from the oven and allow to cool slightly before serving.