Lentil Shepherd's Pie with Sweet Potato Topping

Prep the Sweet Potato Topping

1. Place the sweet potato chunks in a large pot and cover with water. Add a pinch of salt and bring to a boil. Cook for 12 to 15 minutes, or until the potatoes are fork-tender.
2. Drain the sweet potatoes thoroughly. Mash them until smooth, then season with salt and pepper to taste. Set aside.

Cook the Lentil Filling

1. Heat the cooking oil in a large pan over medium heat. Add the chopped onion and diced carrots. Sauté for 6 to 8 minutes, stirring occasionally, until the carrots begin to soften.
2. Stir in the tomato paste and dried thyme, cooking for 1 minute to cook out the raw tomato flavor.
3. Add the drained lentils, crumble in the vegetable stock cube, and pour in 150ml of water. Stir well to dissolve the stock cube. Bring to a gentle simmer and cook for 10 minutes until the mixture has thickened into a rich, saucy filling. Season with salt and pepper to taste.

Assemble and Bake

1. Preheat your oven to 200°C.
2. Transfer the hot lentil filling into an ovenproof baking dish, smoothing it into an even layer.
3. Spoon the mashed sweet potato over the lentils, carefully spreading it to cover the filling entirely. Use the back of a fork to create decorative ridges on top, which will crisp up in the oven.
4. Bake for 20 minutes, or until the sweet potato topping is lightly browned at the edges and the lentil filling is bubbling around the sides. Let it stand for 5 minutes before serving.