To begin, prepare the mashed potatoes. Boil the cubed potatoes in salted water until fork tender, about 15–20 minutes. Drain well and mash until smooth. Add warm milk, butter, and a pinch of salt, stirring until creamy. For a richer topping, whisk in the egg yolk. Set aside.

Preheat your oven to 180°C (350°F). In a large skillet over medium heat, heat the olive oil and sauté the onion, bell pepper, and garlic until softened and fragrant, about 5 minutes. Stir frequently to prevent browning.

Add the ground beef to the skillet, breaking it apart with a wooden spoon. Cook until browned and no pink remains, about 8 minutes. Season with smoked paprika, cumin, oregano, salt, and pepper for a traditional Argentine flavour profile.

Stir in the tomato paste and beef stock, allowing the mixture to simmer gently for 5 minutes until thickened. Adjust seasoning if needed. Turn off the heat and mix in the chopped hard-boiled eggs and sliced olives for added texture and flavour.

Assemble the Pastel de Papa. In a greased ovenproof dish, spread the beef mixture evenly across the bottom. Gently spoon the mashed potatoes over the top, spreading with a spatula to create an even layer. Use a fork to create decorative ridges on the surface, which will crisp beautifully during baking.

For added richness, dot the top of the mashed potatoes with small bits of butter. Place the dish in the preheated oven and bake for 20–25 minutes, or until the top is golden and the filling is bubbling around the edges.

For extra browning, switch the oven to broil for the last 2–3 minutes of baking, keeping a close eye to avoid burning. Once done, remove the dish from the oven and let it rest for 5 minutes before serving.

Serve the Pastel de Papa hot, garnished with fresh parsley for a vibrant touch. Pair it with a crisp green salad or crusty bread to complete the meal. For a traditional Argentine experience, enjoy with a glass of Malbec wine.