Healthy Shepherd's Pie with Sweet Potato Topping

Preheat your oven to 190°C (375°F). Peel and chop 1kg of sweet potatoes into 2-inch chunks. Place them in a large pot, cover with cold water, and bring to a boil. Cook for 15-20 minutes, or until very tender. Drain well.

While the sweet potatoes cook, finely dice 1 large onion, 2 stalks of celery, and 2 medium carrots. Heat 1 tablespoon of olive oil in a large oven-safe pan or Dutch oven over medium-high heat.

Add the 800g lean beef mince to the hot pan and cook, breaking it up with a spoon, until browned all over. Drain any excess fat. Add the diced onion, celery, and carrots to the pan with the mince. Cook for 8-10 minutes, stirring occasionally, until the vegetables have softened.

Stir in 2 tablespoons of tomato paste, 1 tablespoon of Worcestershire sauce, 1 teaspoon of dried thyme, and 1/2 teaspoon of dried rosemary. Cook for 1 minute, stirring constantly. Pour in 2 cups of beef broth and bring to a simmer. Reduce the heat to low, cover, and let it gently simmer for 10-15 minutes to allow the flavors to meld and the sauce to thicken slightly.

Stir in 1 cup of frozen peas and 1 cup of frozen corn. Season the mince mixture with salt and freshly ground black pepper to taste.

Return the drained sweet potatoes to their pot. Add 1/4 cup of low-fat milk, 1 tablespoon of unsalted butter, and season with salt and pepper. Mash until smooth and creamy. For a silkier mash, you can use an immersion blender or a potato ricer.

Spoon the sweet potato mash over the beef mixture in the oven-safe pan, spreading it evenly to cover completely. You can create ridges with a fork for a rustic look.

Bake in the preheated oven for 20-25 minutes, or until the topping is lightly golden brown and the filling is bubbling. Let it rest for 5-10 minutes before serving.