Baked Potato and Mushroom Casserole

This baked Scalloped Potato and Mushroom Casserole is creamy, rich, tasty, and easy to make. A perfect side dish to enjoy during the holidays or all year round.

If you love casseroles, then check out my chicken parmesan casserole and my healthy tuna casserole.

• Versatile side dish: This scalloped potato cheese casserole pairs perfectly with any main dish you can think of especially main proteins like this baked teriyaki salmon or this maple glazed chicken breast recipe.
• Very tasty: I can’t even explain in more simple words how good this baked potato and mushroom casserole dish is. You have got to try it yourself.
• A great make-ahead recipe: You can easily make this ahead the day before. Prep this dish halfway through a day until right before you bake it in the oven.

Ingredients you will need

• Olive oil: or any oil of choice. Avocado oil works
• Mushrooms: there are many types of mushrooms out there you can pick from but I prefer using button mushrooms for this recipe.
• Garlic cloves: do use garlic cloves instead of garlic powder.
• Onion, thinly sliced: Use white or sweet onions. If you only have purple on hand that’s fine.
• Gluten-free flour (or 1/3 cup all-purpose flour)
• Vegetable broth: to keep this dish vegetarian-friendly, use vegetable broth. If you only have chicken stock, you can use it.
• Soy sauce: use low sodium or coconut aminos
• Milk of choice: any milk works, but keep in mind fat-free or dairy-free milk won’t give a rich creamy outcome. But they will still work, and the outcome varies slightly.
• Kosher salt and ground pepper, to taste
• Russet or Gold Potatoes, peeled and thinly sliced
• Grated parmesan cheese, divided; you may grate your own or get store-bought.
• Grated cheddar cheese: use light or gat free. I used cheddar but you may use other types of shredded cheese.
• Optional: freshly chopped parsley, to garnish

How to make potato casserole

• Preheat the oven to 375F. Butter a 9” x 13” baking dish. Set aside.
• Cook the mushrooms: In a rimmed pan, heat the oil. Add the mushrooms and saute for 5-7 minutes, stirring occasionally.
• Add the onions and garlic: Once the excess liquid has evaporated, stir in the onions and garlic and continue to saute for 3-4 minutes.

• Start to make the sauce: Stir in the flour, then pour the broth, little by little, while stirring to remove any lumps. Add the soy sauce, milk, and salt and pepper.

• Cook the mushroom sauce: The gravy will be a bit salty but don’t worry, potatoes will absorb a lot and reduce the salty flavor. Cook until the sauce starts to thicken and coat the back of a spoon. Set aside.
• Prepare the baking dish: Drizzle a bit of oil and grease a 9×13 baking dish.
• Add potatoes to the dish: Layer half of your potato slices and top with half of the mushroom gravy. Stir a bit to get the sauce through the potato slices. Sprinkle half of the grated parmesan cheese.

• Assemble: Repeat with layers and top with the cheddar cheese.
• Bake: Cover the baking dish with aluminum foil and bake for 1 hour; Remove foil and continue to bake uncovered for about 25-30 minutes or until the top is golden-brown.
• Serve: Allow the dish to cool for 15 minutes, then garnish with parsley, if desired

What to serve with potato casserole

• Baked BBQ Chicken Breast
• Honey Mustard Grilled Chicken
• Salsa Fresca Baked Chicken Breast
• Baked Parmesan-crusted salmon
• Creamy Garlic Shrimp
• Baked Honey Sriracha Chicken Breast
• Mediterranean Baked Salmon
• Healthy Shrimp Scampi
• Honey Chipotle Grilled Chicken
• Pan-seared Salmon in Creamy Dill Sauce
• Garlic Butter Chicken

Frequently asked questions

Recipe notes and tips

• Thinly slice the potatoes. Use russet, golden, or Yukon gold potatoes
• Use any mushroom of your choice. I used button mushrooms and prefer it over the others but other types of mushrooms will work. If you want to improvise and use canned mushrooms you can. But of course fresh tastes best.
• You may use avocado oil instead of olive oil, or any other neutral-tasting oil.
• Want to make it ahead? you can. Once you add the sauce over the scalloped potatoes and add some shredded cheese, cover it with foil and place it in the fridge until ready to bake. It will hold for 2 days.
• You do not have to use cheddar cheese. You may use any other cheese of your choice.
• Consider adding some cauliflower florets. This cuts down on the carb content and adds some fiber as well.
• Do not skip covering the casserole while baking. The potatoes need to cook evenly without drying out or burning.

Storage and reheating

• Storing: store leftovers in a sealed container in the fridge for up to 4 days. Or you may freeze for up to 3 months.
• Reheating: It is best to reheat in the microwave. Reheat for 60-90 seconds at a time until it is heated through.

More casserole recipes

• Chicken Cauliflower Rice Casserole
• Healthy Green Beans Casserole
• Spaghetti Casserole
• Cheeseburger Casserole
• Healthy Tuna Casserole
• Chicken Enchilada Casserole
• Easy Zucchini Casserole
• Chicken Broccoli Rice Casserole