Cook the Lentils:
In a large pot, bring 3 cups of water to a boil. Add the rinsed lentils and cook for about 20-25 minutes, or until tender. Drain any excess water and set aside.
Prepare the Vegetables:
In a large skillet, heat the olive oil over medium heat. Add the diced onion and garlic, cooking for 3-4 minutes until softened. Add the carrots and cook for another 5 minutes until they begin to soften.
Make the Filling:
Add the cooked lentils, peas, corn, tomato paste, soy sauce, thyme, rosemary, and vegetable broth to the skillet. Stir to combine and let the mixture simmer for 10-15 minutes, until the vegetables are tender and the mixture thickens. Season with salt and pepper to taste.
Make the Mashed Potatoes:
While the lentil mixture is simmering, bring a large pot of water to a boil and add the diced potatoes. Cook for about 10-15 minutes, or until tender. Drain the water, then mash the potatoes with butter and milk. Season with salt and pepper to taste.
Assemble the Shepherd’s Pie:
Preheat your oven to 400°F (200°C). Transfer the lentil and vegetable mixture into a baking dish. Spread the mashed potatoes evenly over the top of the lentil mixture, smoothing with a spoon or spatula.
Bake:
Place the dish in the oven and bake for 20-25 minutes, or until the top is golden brown and the filling is bubbly.
Serve:
Let the shepherd’s pie cool for a few minutes before serving. Enjoy!