Check the video below for easy visual instructions.Preheat oven to 390° F/200° C and prepare two baking sheets with parchment paper.
Slice each eggplant lengthwise into 4 pieces. Cut the potatoes into 1/2 inch (1 cm) thick slices. Arrange all slices in a single layer on the baking sheets and brush lightly with some olive oil, sprinkle with salt & pepper. Bake in the oven for about 20 minutes or until lightly brown.
Meanwhile, heat 1 tbsp olive oil in a skillet over medium heat. Add the onion & garlic and sauté for about 4-5 minutes. Add the tomato purée, chopped tomatoes, all spices, and salt & pepper to taste. Finally, add the cooked lentils and let simmer on low heat for about 5 minutes.
For the béchamel sauce, add the plant-based milk to a pan/skillet. Mix in the cornstarch, nutritional yeast, salt and pepper, and whisk. Add the vegan butter and bring the mixture to a boil. Let simmer on low heat for a few minutes until it thickens. Whisk continuously. Remove from heat. Check the recipe notes if you don't want to make the béchamel sauce.
Grease a 13"x9" (33x23 cm) or larger baking dish and arrange half of the potato and eggplant slices on the bottom of the baking dish. Top with the lentil mixture, followed by the remaining potato/eggplant slices (see photo above in the blog post). Pour the béchamel sauce on top and spread evenly. Add vegan cheese to taste (optional).
Bake in the oven for about 30 minutes or until golden brown. Garnish with fresh herbs. Enjoy!