This healthy vegetarian lentil casserole is perfect for cozy fall days. It’s filled with lentils and mushrooms in a lightly umami red wine sauce topped with comforting mashed potatoes.
The coziest fall casserole awaits you within this post. I’ve been making this lentil and mushroom filling for a few years now; sometimes I eat it on it’s own, sometimes I use it as a pot pie filling. Other times I cover it with homemade mashed potatoes and call it a casserole!
Since my family (but really mostly my dad) calls me Casserole more often than they call me by my real name (Cassidy), I find it a little ridiculous that I’ve yet to share a true casserole dish on Cozy Peach Kitchen. Not to mention that I grew up on Midwestern casseroles, although they were mostly meaty and cheesey, unlike this vegan lentil casserole.
Okay, so I didn’t exactly grow up on mushrooms and lentils in casserole form, but wow! Is this a tasty casserole or what?
This vegan casserole is basically a Shepherd’s pie, but I refuse to call it that because I’ve never actually made a “real” shepherd’s pie. So. Here we are: Mushroom and Lentil Casserole with Mashed Potatoes (on top)!
To make this mushroom and lentil casserole, start by sauteing celery, onions, carrots, and garlic in a pan until translucent. Add the mushrooms and cook for 6-8 minutes, until most of the liquid from the mushrooms comes out. The mushrooms add a slightly chewy, meaty texture to this lentil casserole.
Combine the veggies and mushrooms with a bit of soy sauce, wine, and tomato paste for a classic beef stew flavor, minus the beef.
I love using red wine in cooking; it intensifies the flavors of the simplest dishes and you don’t even need a fancy wine to make it work. The alcohol cooks off during the cooking process, so no need to worry about the casserole having any true alcohol content.
To thicken the veggie filling add in a slurry of corn starch and water and simmer until thickened. Mix in the cooked lentils and you have yourself a lentil casserole filling.
To make the mashed potatoes you’ll first want to boil quartered and peeled potatoes for 10 minutes, until softened. Drain off the water and return to the dish you boiled the potatoes in. Add the milk of choice, salt and pepper, and butter. Mash away! If you prefer a creamier mashed potato you can add additional liquid during the mashing process.
Layer the lentil mushroom filling into a lightly oiled casserole dish and top with a layer of mashed potatoes. Cover with foil and bake for 30 minutes.
While the flavors of the lentil casserole may deepen in the oven and you get that true casserole shape and dish… I’ll give you a disclaimer:
If you’re short for time, or don’t want to use your oven, you don’t have to bake this into a casserole! Just layer your lentils on a pile of mashed potatoes and call it a meal.
Mushroom and Lentil Casserole
For the Mashed Potatoes
- 5 medium Russet potatoes, peeled and medium diced
- 2 tablespoons butter or vegan butter
- 1/4 cup unsweetened milk of choice, such as soy or cashew milk
- 1/2 teaspoon salt
- fresh ground black pepper, to taste
For the Lentil Casserole
- 3/4 cup dry green lentils, rinsed (makes ~2.5 cups cooked lentils)
- 2 and 1/2 cups water
- 2 teaspoons olive oil
- medium yellow onion, diced
- 2 medium carrots, diced
- 2 stalks celery, diced
- 3 cloves garlic, minced
- 8 ounces cremini mushrooms, quartered and stems removed
- 8 ounces button mushrooms, quartered and steams removed
- 1 tablespoon soy sauce
- 1 tablespoon tomato paste
- 3 tablespoons red wine
- 1 teaspoon dry thyme
- 1 teaspoon dry rosemary
- slurry: 2 tablespoons water mixed with 2 tablespoons corn starch
- Combine the dry lentils and water in a medium sauce pot. Bring to a boil then simmer for 15 minutes, or until lentils are tender. Once cooked, drain off excess liquid if needed.
- Meanwhile, make your mashed potatoes: Cover the diced potatoes with water in a medium saucepan. Boil until softened, about 10 minutes. Drain off the water and return to the pot. Add butter, seasonings, and milk of choice. Mash into mashed potato consistency, adding more liquid as desired.
- Preheat the oven to 350 degrees F.
- In a medium saucepan, heat oil over medium heat. Saute the onions, celery, and carrots for 3-4 minutes. Add the garlic and cook a minute more.
- Add the quartered mushrooms to the pan. Cook for 6-8 minutes, until the mushrooms are softened and have released most of their juices.
- Add the soy sauce, tomato paste, wine, and vegetable broth. Slowly stir in the cornstarch and water slurry. Add the cooked lentils.
- Add the lentil filling to a lightly greased casserole dish (I use 10x10, but most medium sizes will work). Smooth the mashed potatoes on top of the lentils.
- Cover with foil and bake for 30 minutes; take the foil off for the last 10 minutes. Top with parmesan (vegan or not) at this point if desired. Remove from the oven and let cool for 10 minutes before slicing. Enjoy!