1-Pan Mushroom Potato Casserole

A cozy, hands-off, no sauté mushroom potato casserole that needs just 1 pan. Layers of rich mushroom gravy with beans and veggies, layered with crisp garlic herb potatoes that take only minutes to put together as the oven does all the work. (gluten-free with soy-free and nut-free options)

It’s fall, and it’s time for some comfort food. And what’s more comforting than this casserole, which has a stewy mushroom gravy with beans and veggies, topped with potatoes smothered in garlic butter? There are lots of fall herbs, like fresh thyme and sage, and it all comes together really quickly. 

This is a super easy one-pan casserole. No need to sauté or stand around the kitchen for long periods of time cooking the onions and mushrooms. Everything goes right into the baking dish, and the oven does all the work. 

Once the mushroom and onions are cooked, add the beans, herbs and stew ingredients and top them with some sliced potato and bake, and thats it. You get all the fall flavors and a dish that reminds of mashed potatoes and mushroom bourguignon w/o all the work.

It’s comforting, stewy, and perfect for a fall dinner with your family, served with a side salad, garlicky dinner rolls, or some crusty bakery bread. Or serve it however else you like!

Why You’ll Love Mushroom Potato Casserole

• cozy, hearty, stewy beans and veggies in a rich, mushroom gravy
• 1-pan oven recipe, no standing at the stove!
• very little active cooking time
• No cooking the aromatics and potato separately
• naturally nut-free with easy gluten-free and soy-free options

Ingredients

• veggies – For the mushroom-onion layer, you will need mushrooms, onions, carrots and a whole head of garlic. For the stew and topping, you need celery and potatoes.
• olive oil and/or vegan butter – To help the veggies roast and to make the garlic butter topping.
• red wine – If you don’t want to use wine, you can use a mixture of balsamic vinegar and vegetable stock.
• herbs and spices – We are using fresh or dried thyme, dried sage, dried oregano, garlic powder, onion powder, salt, and pepper. You can also top the casserole with fresh parsley and/or basil for even more flavor.
• soy sauce – For gluten-free, use tamari, and for soy-free, use coconut aminos or more wine.
• beans – Use white beans of choice, like cannellini, great northern, or butter beans.
• stock – Makes the gravy in the baking pan.
• cornstarch – To thicken the gravy. You can use flour instead, if you prefer.
• lemon juice – For moisture and tang in the potato topping.

How to Make Mushroom Potato Casserole

Preheat the oven to 410°F (210°C), and grease a 10×13” or similar-sized baking dish. Chop all your veggies, and grease your baking dish. Slice off about 1/3 from the top of the garlic bulb, so that the cloves are exposed. Reserve the small pieces of garlic cloves from the top third.

Add the reserved small pieces of garlic (peeled) along with the mushrooms, onion, and carrots, 2 teaspoons of the olive oil, and the salt, pepper, and red wine to the baking dish. Mix well to coat, and spread the veggies out evenly. Make some space in the center of the dish, and place the garlic bulb, cut-side-up, in the middle. Drizzle the remaining olive oil over the exposed cloves. Cover the entire dish with a sheet of parchment paper, letting it rest loosely over the top.

Bake for about 40 minutes, or until the mushrooms are al dente and starting to turn golden, and the onions are translucent or starting to turn golden. Check at the 30-minute mark, and stir if anything seems to be scorching. The mushrooms will usually release plenty of moisture, but if the pan is drying out, add a splash of extra stock at that point.

Remove the dish from the oven. Take out the garlic bulb, and set it aside to cool. Add all the herbs, salt, tomato paste, and soy sauce to the baking dish. Mix well, pressing the tomato paste into the mixture, so there are no clumps.

Stir everything together until evenly coated. Add the celery and beans, then mix the cornstarch or flour into the stock and pour it into the pan. Stir well to coat, and spread the mixture evenly with a spatula.

Arrange the sliced potatoes on top of the bean stew mixture, overlapping them slightly.

Squeeze the delicious roasted garlic cloves from the bulb into a small bowl. Add the vegan butter or olive oil, oregano, lemon juice, and a pinch of salt, if using oil. Mash and mix until creamy.

Spread dollops of this garlic butter over the potatoes and smooth lightly. Reserve a little of the mixture for serving later, if desired.

Cover the dish again with parchment and bake for 20 minutes. Remove the parchment and continue baking for another 20 to 25 minutes, or until the potatoes are tender and golden on top. Brush the finished potatoes with the reserved garlic butter.

Sprinkle with fresh herbs, like parsley or basil, before serving. Serve this delicious stew as-is or with a side salad, dinner rolls, or toasted sourdough.

What to Serve with Mushroom Potato Casserole

Serve this delicious stew as-is or with a side salad, dinner rolls, or toasted sourdough.