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This Creamy Mushroom Spinach & White Bean Potato Casserole is the kind of vegetarian comfort food that makes a satisfying dinner. Layers of tender Yukon Gold potatoes bake with savory mushrooms, white beans, and spinach in a rich Alfredo cream sauce. A golden, cheesy topping finishes everything off. It’s hearty, filling, and a nice change from the usual potato casserole.
If you’re looking for a meatless dinner that feels like a real comfort-food meal, this is a great one to add to your rotation. The white beans make it extra hearty, and the leftovers are just as good the next day. This casserole will quickly become a favorite.
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Health benefits
This mushroom, spinach, and white bean potato casserole offers a nice combination of vegetables, plant-based protein, and satisfying carbohydrates. White beans provide plant protein and dietary fiber, which help make the dish filling and support digestive health. Mushrooms provide B vitamins and minerals, while spinach contributes vitamins A, C, and K, along with folate and iron. Potatoes provide potassium, vitamin C, and energy from carbohydrates.
Although the Alfredo sauce, heavy cream, and cheese make this a richer casserole, the beans and vegetables add nutritional value and make it more substantial than a traditional cheesy potato bake. It’s a satisfying vegetarian dinner that combines several food groups in one dish.
How to make
The full Vegetarian potato casserole recipe with ingredient amounts and instructions is in the printable recipe card below. I have tips, tricks, and serving suggestions for you in the post.
This casserole is nicely filled with lots of mushrooms. The 1 pound 4 ounces measurement is what my grocery store sells for the package size. But really, if you have a little more or a little less, that’ll work just fine.
Cooking the mushrooms: Give the mushrooms enough time to release their moisture and brown. Don’t rush this step. Cooking off their moisture helps concentrate their savory flavor and prevents excess liquid from making the casserole watery.
White beans: Cannellini or Great Northern beans would both be good choices. I typically buy cannellini because I can get the cans in low sodium, but either will work.
Choosing the potatoes: Yukon Gold potatoes are my first choice for this casserole. They have a naturally creamy texture, buttery flavor, and and hold their shape well during baking. Russet potatoes also work, but I recommend peeling them because their skins can be thicker.
Slicing the potatoes: Try to keep the potato slices about ¼ inch thick and as uniform as possible. This helps them cook evenly. A mandoline slicer is helpful (just use it carefully), but a sharp knife works, too. Thicker slices may need additional baking time.
Seasoning the layers: Potatoes need seasoning, so add a little salt and pepper as you layer them. Alfredo sauce and Parmesan already contain salt, so start lightly and adjust to your taste. You can always add more salt when you serve the dish, but you can’t take it out.
Covering the creamy mushroom casserole: Cover the dish tightly with foil or a tight-fitting lid before baking. This traps steam and helps the potatoes become tender. Remove the foil or lid only when you’re ready to brown the cheese. Cover tightly while baking
Checking for doneness: Baking time can vary depending on the thickness of the potato slices and your oven. Test the center of the casserole with a knife. The potatoes should be completely tender before you broil the cheese.
Broil at the end: The final few minutes give the mozzarella a golden, bubbly finish. Keep a close eye on it so it doesn’t burn.
Serving suggestions
This is a hearty vegetarian casserole that works well as a main dish. Here are some good ways to serve it:
- Green salad: A simple mixed green salad with a soy vinaigrette balances the creamy sauce.
- Roasted vegetables: Serve with roasted broccoli, green beans, asparagus, or Brussels sprouts.
- Crusty bread: Garlic bread, buttermilk biscuits, or a crusty no knead bread is great for soaking up the creamy sauce.
- Tomato salad: Fresh tomatoes with basil and a light vinaigrette provide a nice contrast.
- Holiday dinner: This casserole makes a lovely vegetarian option for Thanksgiving, Christmas, or other family gatherings.
Storage and reheating tips
Allow the Vegetarian Mushroom, Spinach & Potato Gratin to cool, then transfer the leftovers to an airtight container or cover the baking dish tightly. Refrigerate for up to 3–4 days.
You can freeze leftovers in airtight, freezer-safe containers for up to 2 months. Keep in mind that cream-based sauces and potatoes can change texture slightly after freezing. The sauce may separate a little, and the potatoes may become softer.
Reheat individual portions of this Cheesy Mushroom and Potato Casserole in the microwave until heated through. For larger portions, cover with foil and warm in a 350° F oven until hot in the center. Add a splash of cream or milk if the sauce seems too thick.
Make ahead: You can prepare the mushroom, spinach, and white bean mixture a day ahead and refrigerate it separately. For the best potato texture, slice and assemble the casserole shortly before baking. If baking directly from the refrigerator, allow extra time and check that the center is hot and the potatoes are tender.
Frequently asked questions
Can I use a different type of potato?
Yes, you can use a different potato. Yukon Gold potatoes are my first choice because they have a creamy texture, buttery flavor, and hold their shape well during baking. Russet potatoes also work. I recommend peeling Russets because their skins tend to be thicker. Keep the slices about ¼ inch thick regardless of which potato you use.
Can I make this mushroom potato casserole ahead of time?
Yes, this Creamy Mushroom Spinach Potato Bake is make ahead friendly. For the best results, prepare the mushroom, spinach, and white bean mixture ahead of time and refrigerate it separately. Assemble the casserole with freshly sliced potatoes shortly before baking. This helps prevent the potatoes from discoloring and keeps their texture at its best.
Can I use frozen spinach instead of fresh spinach?
Yes. Thaw the frozen spinach completely and squeeze out as much excess water as possible before adding it to the mushroom mixture. This is important because extra moisture can make the casserole watery. Use approximately ¾ to 1 cup of thawed, well-drained spinach in place of the 5 ounces of fresh baby spinach.
More Vegetarian comfort food
I think that easy vegetarian meatless casserole recipes are the perfect comfort food for vegetarians and meat eaters alike. Check out my Chili Mac Casserole, Broccoli Rice Casserole, Gnocchi Casserole, and Broccoli Wild Rice Casserole for more delicious comfort food.
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Recipe
Creamy Mushroom Spinach & White Bean Potato Casserole
Equipment
- 9 x 13-inch casserole dish
- Large skillet
- Mixing bowl
- Aluminum foil
Ingredients
- 1 tablespoon oil
- 1 tablespoon butter plus more for greasing the casserole dish
- 1 pound 4 ounces fresh mushrooms sliced (567 g)
- 2 garlic cloves finely diced or pressed or ¼ teaspoon garlic powder
- 1 yellow onion diced
- 1 tablespoon dried thyme
- ½ teaspoon salt plus additional salt for seasoning the potatoes
- ¼ teaspoon black pepper plus additional pepper for seasoning the potatoes
- 15 ounces canned low sodium white beans drained and rinsed
- 5 ounces baby spinach 140g
- 15 ounces jarred Alfredo sauce
- 1 cup heavy cream
- 1½ pounds Yukon Gold potatoes thinly sliced about ¼ inch thick
- ¼ cup shredded Fresh Parmesan cheese
- 8 ounces fresh mozzarella pearls
Instructions
- Preheat the oven to 360° F. Generously butter a 9×13 inch casserole dish, and set aside.
- Heat the oil and butter in a large skillet over medium-high heat. Add the sliced mushrooms and cook, stirring occasionally, for about 10 minutes, or until they release their liquid and the liquid evaporates. Continue cooking until the mushrooms are lightly browned.1 tablespoon oil, 1 tablespoon butter, 1 pound 4 ounces fresh mushrooms
- Add the garlic, diced onion, thyme, ½ teaspoon salt, and ¼ teaspoon black pepper. Cook for about 10 minutes, stirring occasionally, until the onion softens.2 garlic cloves finely diced or pressed, 1 yellow onion, 1 tablespoon dried thyme, ½ teaspoon salt, ¼ teaspoon black pepper
- Stir in the drained and rinsed white beans. Add the spinach a handful at a time, stirring until wilted before adding more. Remove the skillet from the heat.15 ounces canned low sodium white beans, 5 ounces baby spinach
- In a medium bowl, stir together the Alfredo sauce and heavy cream until combined.15 ounces jarred Alfredo sauce, 1 cup heavy cream
- Arrange the sliced potatoes in the prepared casserole dish. Season each layer lightly with salt and pepper.1½ pounds Yukon Gold potatoes
- Spread the mushroom, spinach, and white bean mixture evenly over the potatoes. Pour the Alfredo cream sauce over the top, making sure the potatoes and vegetables are well covered. Sprinkle with Parmesan and mozzarella pearls, distribute them evenly so each serving gets some cheesy topping.¼ cup shredded Fresh Parmesan cheese, 8 ounces fresh mozzarella pearls
- Cover the casserole tightly with foil or a tight-fitting lid. Place the dish on a rimmed baking sheet to catch any sauce that bubbles over. Bake for 90 minutes, or until the potatoes are tender when pierced with a knife.
- Remove the foil or the lid and place the casserole under the broiler for 3–5 minutes, or until the cheese is lightly browned. Watch carefully to prevent burning.
- Let the casserole stand for 10 minutes before serving. This gives the sauce time to settle and makes serving easier.
Notes
Nutrition
Nutritional information is based on third-party calculations, and should be considered estimates. Actual nutritional content will vary based on brands used, measuring methods, portion sizes, and more.
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