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top view of a white dish with creamy potato and mushroom casserole with spoon in the dish
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5 from 1 vote

Baked Potato and Mushroom Casserole

This potato casserole dish is tasty, easy to make, and made with potatoes, mushrooms, onions, shredded cheese, and other simple ingredients. Ready in just one hour. A perfect side dish to serve all year round.
Prep Time15 minutes
Cook Time1 hour 30 minutes
Total Time1 hour 45 minutes
Course: Side Dish
Cuisine: American
Diet: Vegetarian
Servings: 8
Author: Rena

Equipment

  • 9” x 13” baking dish
  • knife
  • pan or skillet
  • cutting board

Ingredients

  • 3 tablespoons olive oil or avocado oil
  • 1 pound mushrooms sliced
  • 4-6 garlic cloves pressed
  • 1 medium onion thinly sliced
  • 3 tablespoons gluten-free flour or 1/3 cup all-purpose flour
  • 3/4 cup vegetable broth
  • 1/4 cup soy sauce
  • 2 cups milk of choice I used 2 %
  • Kosher salt and ground pepper to taste
  • 2 pounds Russet or Gold Potatoes peeled and thinly sliced
  • 1 cup grated parmesan cheese divided
  • 1 cup grated cheddar cheese
  • Optional: freshly chopped parsley to garnish

Instructions

  • Preheat the oven to 375F. Butter a 9” x 13” baking dish. Set aside.
  • In a rimmed pan, heat the oil. Add the mushrooms and saute for 5-7 minutes, stirring occasionally. Once the excess liquid has evaporated, stir in the onions and garlic and continue to saute for 3-4 minutes.
  • 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.
  • 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.
  • Drizzle a bit of oil and grease a 9x13 baking 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.
  • Repeat with layers and top with the cheddar cheese.
  • 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.
  • Allow the dish to cool for 15 minutes, then garnish with parsley, if desired.

Notes

  • use any milk of your choice 
  • russet or golden yellow potatoes work
  • any mushroom of your choice, button mushrooms will be optimal
  • Use low-fat cheese if possible 
  • Nutritional values are just an estimation that is calculated automatically. Values may vary

Nutrition

Calories: 306kcal | Carbohydrates: 32g | Protein: 14g | Fat: 15g | Saturated Fat: 6g | Polyunsaturated Fat: 1g | Monounsaturated Fat: 6g | Cholesterol: 28mg | Sodium: 873mg | Potassium: 822mg | Fiber: 3g | Sugar: 6g | Vitamin A: 414IU | Vitamin C: 9mg | Calcium: 310mg | Iron: 2mg