Vegetarian Cottage Pie with Lentil and Root Vegetable Filling

Preheat oven to 375°F (190°C).

Place cubed sweet potatoes in a large pot, cover with water, and bring to a boil. Cook until tender, about 15-20 minutes. Drain well and set aside.

While sweet potatoes are cooking, heat olive oil in a large skillet or Dutch oven over medium heat. Add onion, carrots, and celery and cook until softened, about 5-7 minutes.

Add garlic and cook for 1 minute more, until fragrant.

Stir in lentils, vegetable broth, tomato paste, thyme, rosemary, bay leaf, vegetarian Worcestershire sauce (if using), salt, and pepper. Bring to a boil, then reduce heat and simmer, covered, for 20-25 minutes, or until lentils are tender and the sauce has thickened.

Remove bay leaf.

While the lentils are simmering, mash the cooked sweet potatoes with butter and milk (or plant-based milk) until smooth and creamy. Season with salt, pepper, and a pinch of nutmeg (if using).

Pour the lentil and vegetable filling into a baking dish. Top with the mashed sweet potatoes, spreading evenly.

Bake for 20-25 minutes, or until the sweet potato topping is lightly golden brown and the filling is bubbly.

Let cool for a few minutes before serving.