Loaded Leftover Mashed Potato Soup (Pantry & Freezer Clean-Out)

I am officially convinced that leftover mashed potatoes exist for one reason only: to become soup. This recipe started on one of those nights where I had a 28-ounce container of mashed potatoes, a random bag of O’Brien hash browns with more air than potatoes, a packet of instant mash, and some precooked chicken and bacon hiding in the fridge. Instead of doing the “there’s nothing to eat” sigh at the stove, I dumped it all in a pot and hoped for the best.

What came out was a thick, cozy, loaded potato soup that tastes like a baked potato, hashbrown casserole, and chowder all had a very comforting little baby together. It is creamy from the mashed potatoes, hearty from the diced potatoes and chicken, and smoky from the bacon. And because everything is already cooked, it comes together way faster than starting from raw potatoes.

This leftover mashed potato soup is also incredibly forgiving. If your container is extra full, it still works. If your hash brown bag is nearly empty, that works too. You can bulk it up with instant potatoes, thin it out with extra milk, and toss in whatever protein you have hanging around. It is very “use what you have” friendly, which is basically my entire cooking personality at this point.

So if you are staring at cold mashed potatoes and mystery freezer bags wondering what to do, this is your sign: we’re turning all of it into a big pot of comfort that feeds the whole house with almost no effort.

Loaded Leftover Mashed Potato Soup Recipe

Ingredients

Base Soup

• 1 (28-ounce) container leftover mashed potatoes (about 3 to 3 1/2 cups)
• 3 cups milk to start, plus more as needed to thin
• 1 tablespoon butter (optional, but adds richness)
• 1 to 1 1/2 cups frozen O’Brien diced hash browns (potatoes with onions and peppers)
• 1 cup shredded cheese (cheddar or whatever you have)
• 1 (about 4-ounce) packet roasted garlic instant mashed potatoes (such as Idahoan), used as needed for thickening

Optional Extras

• 1 cup frozen seasoned roasted potatoes, roughly chopped if the pieces are large
• Additional plain instant mashed potatoes (from a box) if you want it even thicker

Seasonings

• 1 to 1 1/2 teaspoons garlic powder
• 1 teaspoon onion powder
• 1/2 teaspoon paprika (optional)
• Salt and black pepper to taste
• 1 teaspoon chicken bouillon or Better Than Bouillon, optional but very good

Protein Add-Ins (Optional but Delicious)

• 1 to 2 cups precooked diced chicken (frozen is fine)
• 1/2 to 3/4 cup refrigerated bacon crumbles

For Serving (Optional)

• Extra shredded cheese
• Sour cream or plain Greek yogurt
• Sliced green onions or chives
• Extra crispy bacon crumbles

Instructions

Build the base. Add the leftover mashed potatoes to a large soup pot. Pour in 3 cups of milk and add the butter if using. Turn the heat to medium and stir frequently until the mashed potatoes loosen up and everything looks creamy and smooth. If it is so thick your spoon stands straight up, you can splash in a little more milk right away.

Add the frozen potatoes. Stir in the frozen O’Brien hash browns. If you are using the seasoned roasted potatoes, add about 1 cup of those as well. Let the soup simmer on medium-low for about 10 minutes, stirring occasionally, so the potatoes soften and start to break down into the soup.

Season the soup. Add the garlic powder, onion powder, paprika (if using), chicken bouillon, and a small pinch of salt and pepper. Stir well. Let the soup gently bubble for another 3 to 5 minutes so the flavors start to come together.

Melt in the cheese. Add 1 cup shredded cheese and stir until it is completely melted and the soup looks glossy and creamy. At this point, taste and adjust the seasonings. You can always add more garlic, onion powder, salt, or pepper if it needs a little extra something.

Thicken with instant potatoes as needed. Open the packet of roasted garlic instant mashed potatoes. Sprinkle in about 1/4 of the packet and stir well. Give it a minute to sit and thicken; instant potatoes work fast. If you want the soup thicker, add more in small amounts, stirring and waiting between each addition until you reach your favorite consistency.

If you accidentally go overboard and it turns into potato cement, just pour in a bit more milk and stir until it loosens back up. You can also use a tablespoon or two of the plain boxed instant potatoes the same way if you want an even thicker chowder-style soup.

Add the precooked chicken. Once the soup is thick and bubbling gently, stir in 1 to 2 cups of precooked diced chicken (it can go in frozen). Let it simmer for about 5 to 7 minutes, or until the chicken is heated through and tender. Since it is already cooked, you are just warming it up, not actually cooking it from raw.

Add the bacon. Stir 1/2 to 3/4 cup bacon crumbles directly into the pot during the last 2 to 3 minutes of cooking if you like them soft and smoky in the soup. For crispier bacon, you can warm the crumbles in the microwave for 20 to 30 seconds and save some to sprinkle over each bowl when serving.

Adjust the final texture. Take a look at your soup and decide how you like it. If it is too thick, add a splash or two of milk until it reaches the perfect creamy spoonable consistency. If it is still thinner than you want, sprinkle in another spoonful of instant potatoes and stir again.

Serve. Ladle the soup into bowls and top with extra cheese, a spoonful of sour cream, green onions or chives, and a little more bacon if you have it. Serve hot with bread, biscuits, or whatever carbs are currently calling your name.

Recipe Notes and Variations

• If your leftover mashed potatoes were already heavily seasoned or made with sour cream or cream cheese, you may need less added salt. Taste as you go and adjust gently.
• For a smoother soup, you can use an immersion blender for a few quick pulses before adding the chicken and bacon. I like to leave it mostly chunky so you still get bites of potato.
• If you do not have roasted garlic instant potatoes, any flavor of instant mashed potatoes will work. Just keep an eye on the salt if you use a very seasoned variety.
• This soup reheats really well. It will thicken in the fridge, so when you warm it up, just add a splash of milk or water and stir until it loosens back to soup consistency.

Closing Thoughts

This loaded leftover mashed potato soup is one of those recipes that feels a little bit like cheating in the best way. You are not starting from scratch or peeling potatoes for an hour; you are taking what is already in your fridge and freezer and turning it into a completely new meal that tastes like you planned it that way.

It is also a great way to stretch leftovers for a big family or a hungry crew without anyone feeling like they are eating the same thing twice. The mashed potatoes become the base, the hash browns and roasted potatoes add texture, and the chicken and bacon make it hearty enough to count as a full dinner. Nobody sees “clean-out night” on the table; they just see a big bowl of cozy, cheesy potato goodness.

If you end up making your own version with different mix-ins or seasonings, feel free to experiment. This is a very forgiving, “use what you have” kind of soup, and that is exactly the kind of recipe that earns a permanent spot in my Mom Unfiltered kitchen rotation.