Arrange the eggplant in a single layer on 2 baking sheets and sprinkle with salt. Let the eggplant sit for 30 minute to 1 hour.
Preheat the oven to 375°F (190°C).
Remove the eggplant slices from the baking sheets and squeeze the water from the slices. Dry the baking sheets and line them with parchment paper.
In a large mixing bowl, toss the eggplant with olive oil, oregano, and pepper.
Spread the eggplant out in a single layer on one of the prepared baking sheets and bake for 25 minutes, flipping halfway through.
For the potatoes
In a large mixing bowl, toss the potatoes with the olive oil, salt, oregano, and pepper.
Spread the potatoes in a single layer over the second baking sheet lined with parchment paper. Bake for 20 minutes, flipping halfway through (I just bake them right alongside the eggplant).
To make the lentils (do this while the veggies are roasting)
Combine the lentils, water, salt, and pepper in a saucepan. Bring the water to a boil.
Reduce the heat to low, cover the pot, and simmer for 15 minutes or until the lentils are just tender. Drain any excess liquid.
Make the sauce (do this while the lentils are cooking)
Heat the olive oil over medium-high heat in a large, heavy-bottomed saucepan. Add the onion, season with salt, and saute until translucent. Add the garlic and saute until fragrant.
Add the cinnamon, nutmeg, thyme, and oregano to the saucepan. Saute for a few seconds. Add the tomato paste and saute for 30 seconds or until darkened in color.
Add the wine and cook for 1 minute or until the wine has evaporated. Stir with a wooden spoon occasionally, knocking any brown bits off of the bottom of the pan.
Stir the lentils and mushrooms into the sauce. Saute for 5 minutes.
Stir in the crushed tomatoes and bay leaves and bring the sauce to a boil. Reduce the heat to low and let the sauce simmer for 20 minutes.
Taste the sauce and season with salt and pepper to taste. Stir in the parsley.
To make the bechamel (do this while the sauce is simmering)
Melt the butter over medium heat in a medium-sized, heavy-bottomed saucepan. Whisk in the flour and cook for 1 minute, whisking continuously.
Gradually whisk in the plant milk until smooth. Turn the heat to low and let the sauce simmer until thickened (about 5 minutes).
Stir in the nutritional yeast and nutmeg. Taste the sauce and season with salt and pepper as desired. Turn off the heat and set aside.
Assemble
Liberally grease a 9X13-inch casserole dish and preheat the oven to 375°F (190°C) if you turned it off after roasting the eggplant and potatoes.
Arrange the roasted potato slices in the bottom of the casserole dish. It’s ok to have some overlap. Top the potatoes with half of the sauce. Arrange the roasted eggplant over the sauce. It’s ok to have some overlap. Spread the remaining sauce over the eggplant. Spread the bechamel over the final sauce layer.
Bake for 50 minutes or until golden brown.
If you want your bechamel to get an extra golden brown hue to it, pop the casserole under the broiler for a minute or two at the end of the baking time.
Notes
To store: Leftover vegan moussaka can be stored in an airtight container in the refrigerator for up to 4 days. To reheat, use the microwave or warm up larger portions in a 350ºF oven until heated through.To freeze: For longer storage, you can freeze individual portions of this vegan moussaka in airtight containers for up to 3 months. To reheat, thaw in the refrigerator overnight and then follow the reheating instructions above.