Mom’s Thrifty Potato Casserole

A comforting family-table dish made with homemade cream of mushroom soup.

 

Buying condensed soups isn’t as budget-friendly as it once was, and my mom knew that long before it became common conversation. When she was short on time, she’d reach for a store-bought can—but when she had a few extra minutes, she made her own cream of mushroom soup from scratch. It was simple, hearty, and full of flavor.

This casserole-style dish is one of those comforting meals that fed a family well without fuss. Thinly sliced potatoes, onions, peas, and cheese come together with a creamy mushroom base to create a warm, satisfying supper—proof that homemade doesn’t have to be complicated to be delicious.

Ingredients:  

1 onion, cut in half and thinly sliced
5–6 potatoes, peeled and thinly sliced
1/2 tsp. salt
1 package (10 ounces) frozen peas
2 c. shredded sharp cheddar cheese, divided
1 can condensed cream of mushroom soup or homemade (recipe below)
1 soup can milk

Homemade Cream of Mushroom Soup Ingredients:

1/4 c. butter
1 (8-ounce) can mushrooms, drained and finely chopped
1/3 c. flour
1/2 tsp. garlic powder
1/4 tsp. onion powder
1/4 tsp. black pepper
1/4 tsp. salt
1 cup chicken broth
1 cup milk

Directions:  

Melt the butter in a medium saucepan over medium-low heat.

Add the chopped mushrooms, garlic powder, onion powder, pepper, and salt. Stir and cook for 2–3 minutes until fragrant.

Sprinkle the flour over the mushroom mixture and stir well to combine. Cook for about 1 minute to remove the raw flour taste.

Slowly pour in the chicken broth, stirring constantly to prevent lumps.

Gradually add the milk, continuing to stir until smooth.

Bring the mixture to a gentle simmer. Cook for 2–3 minutes, stirring often, until thickened.

Remove from heat and set aside until ready to use.
Note: The soup will continue to thicken as it cools.

Assemble the Casserole

Preheat the oven to 350°F.  Lightly grease a 9 x 13-inch casserole dish or similar 3-quart baking dish.

Layer half of the sliced potatoes in the bottom of the dish, followed by half of the sliced onions. Sprinkle lightly with salt.

Scatter the frozen peas evenly over the layers.

Spoon the homemade cream of mushroom soup evenly over the vegetables and gently spread it out.
If using canned soup, whisk the condensed soup and 1 soup can of milk together first, then pour over the potatoes and onions. This step helps the sauce spread evenly through the casserole, just the way Mom used to do it

Sprinkle 1 1/2 cups of the shredded cheddar cheese over the top.

Repeat with remaining potatoes and onions, then top with the remaining 1/2 cup of cheese.

Cover with a lid or a sheet of foil.

Bake for 45–50 minutes, or until the potatoes are tender.

Remove the lid or foil and bake an additional 10–15 minutes, until bubbly and lightly golden. Serve and enjoy.

Notes: 

Milk substitutions: canned milk, half-and-half, or heavy cream all work well. 

You may want to put a baking sheet beneath the casserole dish just in case it bubbles over.  The baking sheet will catch the spills.