Sweet Potato Lentil Burgers with Mushroom-Onion Topping

Steps

1. Put the lentils and water in a saucepan, bring to a boil, then simmer 20 to 25 minutes until tender. Drain well and let cool 10 minutes.
2. While the lentils cook, peel and grate the sweet potato and carrot, mince the garlic, slice the mushrooms and onion, and wash and dry the romaine leaves and slice the tomato.
3. Preheat the oven to 400°F (200°C) and line a baking sheet with parchment.
4. In a large bowl, mash the cooked lentils roughly with a fork. Add the sweet potato, carrot, oats, egg, garlic, paprika, cumin, half the salt and the black pepper, and mix well. Let rest 5 minutes so the oats absorb moisture.
5. Shape the mixture into 8 patties about 3/4 inch thick and set them on the baking sheet. Brush the tops with half the olive oil.
6. Bake 15 minutes, flip carefully, and bake 12 to 15 minutes more until browned and firm and the center reaches 160°F (71°C).
7. Meanwhile, heat the remaining half of the olive oil in a large skillet over medium heat. Add the onion and cook 10 minutes, stirring often, until soft and golden.
8. Add the mushrooms, thyme and the remaining half of the salt to the onion and cook 8 to 10 minutes until the mushrooms are browned and their liquid has cooked off. Stir in the balsamic and cook 1 minute more.
9. To serve, lay two romaine leaves per burger, add a patty, spread with the mustard, top with the tomato and spoon the mushroom-onion mixture over. Wrap and enjoy, two burgers per person.