Name: Leftover Garlic Mashed Potato Soup
Prep time: 10 min
Cook time: 20 min
Total time: 30 min
Cuisine: American
Ingredients: 2 ½ cups leftover garlic mashed potatoes; 1 medium onion, chopped; 2 cloves garlic, minced; 2 tablespoons butter; 2 ½ to 3 cups chicken or vegetable broth; 1 cup whole milk or cream; 1 cup shredded cheddar cheese; ½ teaspoon salt; ¼ teaspoon black pepper; 1 tablespoon chopped fresh thyme or parsley

One of my favorite things to do after a big holiday meal is to reinvent the leftovers, and this Leftover Garlic Mashed Potato Soup is one of my go-to transformations. It’s creamy, comforting, and packs all the garlicky goodness of yesterday’s mashed potatoes into a warm bowl of cozy joy. There’s something deeply satisfying about taking something as humble as leftovers and turning it into something crave-worthy.

This soup doesn’t just use up leftovers—it elevates them. The mashed potatoes become the velvety base, while sautéed onions and garlic add depth, and a touch of broth brings everything together. Top it off with sharp cheddar and fresh herbs, and suddenly, yesterday’s side dish becomes today’s main event.

Why You’ll Love This Leftover Garlic Mashed Potato Soup

It’s the perfect way to use up leftover mashed potatoes.
Comes together in under 30 minutes.
Comfort food that doesn’t feel like a repeat.
Easily adaptable with add-ins like bacon, chives, or cream.
Freezer-friendly for later cravings.

Can I Use Any Type of Mashed Potatoes?

Absolutely! While this recipe works especially well with garlic mashed potatoes for added flavor, any leftover mashed potatoes will do. If your potatoes were made with cream or butter, even better—it’ll give the soup a rich, luxurious texture. Just avoid potatoes that are overly dry or stiff, as they’ll need extra liquid to smooth out.

Options for Substitutions

Broth: Use chicken, vegetable, or even bone broth. For a richer taste, try a mix of broth and a splash of cream.
Cheese: Sharp cheddar is my favorite, but you can use gouda, parmesan, or any meltable cheese.
Milk/Cream: Whole milk, half and half, or heavy cream all work here depending on how indulgent you want it.
Herbs: Thyme, rosemary, or parsley all complement the potato base beautifully.
Add-ins: Bacon bits, sautéed mushrooms, or even roasted corn add texture and depth.

Ingredients for this Leftover Garlic Mashed Potato Soup

Leftover garlic mashed potatoes – The creamy, garlicky base that gives this soup its bold flavor and silky texture.
Onion – Adds a sweet and savory backbone when sautéed.
Garlic – Fresh garlic intensifies the flavor already present in the mashed potatoes.
Butter – For sautéing and adding richness.
Chicken or vegetable broth – Helps thin out the mashed potatoes into a soup consistency while adding depth.
Milk or cream – Balances the broth and mashed potatoes, making the soup creamy and smooth.
Cheddar cheese – Brings sharpness and richness to the final dish.
Salt and pepper – Essential for seasoning and balancing the flavors.
Fresh herbs (thyme or parsley) – For a finishing touch of freshness.

Step 1: Sauté the Aromatics

Start by melting butter in a large pot over medium heat. Add chopped onion and cook until softened, about 5–7 minutes. Stir in minced garlic and cook for another 1–2 minutes, just until fragrant.

Step 2: Add the Mashed Potatoes

Stir in your leftover garlic mashed potatoes. The mixture will be thick at first, so gently break it apart with a wooden spoon or spatula to combine with the sautéed aromatics.

Step 3: Pour in Broth and Stir

Slowly add in the broth while stirring to loosen up the mashed potatoes. Start with 2 cups and add more as needed to get your desired soup consistency. Bring everything to a low simmer.

Step 4: Stir in Milk or Cream

Once the soup is simmering and smooth, pour in milk or cream. This step makes the soup ultra-creamy and rounds out the garlic flavor. Continue to simmer on low heat for about 5–10 minutes, stirring occasionally.

Step 5: Add Cheese and Seasonings

Reduce the heat and stir in shredded cheddar cheese until melted and incorporated. Taste and season with salt and black pepper. Add more cheese if you love it extra cheesy.

Step 6: Blend for Smoothness (Optional)

If you prefer a silky-smooth soup, use an immersion blender to blend the mixture directly in the pot. Alternatively, blend in batches using a standard blender—but be careful with hot liquids!

Step 7: Garnish and Serve

Ladle the soup into bowls and top with more shredded cheese, fresh herbs, and optionally a sprinkle of crispy bacon or green onions. Serve warm with crusty bread or a side salad.

How Long to Prepare the Leftover Garlic Mashed Potato Soup

This soup is a time-saver, which is one of the reasons I love making it on busy weeknights.

Prep Time: Since the mashed potatoes are already cooked, prep is minimal. Chopping onions and garlic and gathering your ingredients takes about 10 minutes.

Cooking Time: The actual cooking takes around 20 minutes. It’s just enough to sauté the aromatics, warm the mashed potatoes, and let everything blend together with the broth and cheese.

Tips for Perfect Leftover Garlic Mashed Potato Soup

Warm the mashed potatoes slightly before adding to the pot – This makes them easier to incorporate with the broth.
Use a whisk after adding the broth – Helps break up any clumps and creates a smoother texture.
Adjust the liquid as needed – Some mashed potatoes absorb more liquid than others; don’t hesitate to add more broth.
Use fresh herbs last – Stir in chopped herbs just before serving for best flavor.
Taste as you go – Since leftovers vary, always taste for seasoning and adjust.

Watch Out for These Mistakes While Cooking

Adding all the broth at once – This can result in overly thin soup. Add gradually to control consistency.
Overheating the cheese – High heat can cause cheese to separate. Stir it in off-heat or on low.
Skipping seasoning – Mashed potatoes are already seasoned, but once diluted with broth and milk, more salt or pepper is often needed.
Not blending when needed – If your potatoes were chunky, blending will help avoid a lumpy soup.
Overcooking the garlic – Burned garlic turns bitter. Add it after onions are translucent.

What to Serve With Leftover Garlic Mashed Potato Soup?

1. Crusty Bread

A slice of toasted sourdough or baguette is perfect for dipping into this creamy soup.

2. Green Salad

A simple salad with vinaigrette adds brightness and balances the richness of the soup.

3. Grilled Cheese Sandwich

Pair with a golden, crispy grilled cheese for a classic comfort combo.

4. Roasted Vegetables

Add a tray of roasted Brussels sprouts, carrots, or broccoli for more texture and nutrition.

5. Bacon-Wrapped Asparagus

A savory, crispy side that complements the creamy garlic flavors beautifully.

Storage Instructions

Refrigeration: Store any leftover soup in an airtight container in the refrigerator for up to 4 days. Reheat gently on the stove over low heat, adding a splash of broth or milk if it has thickened too much.

Freezing: Yes, you can freeze this soup! Let it cool completely, then pour into freezer-safe containers. It will keep for up to 2 months. Thaw overnight in the fridge and reheat gently.

Estimated Nutrition

(Per 1-cup serving, approximate)

Calories: 280
Protein: 8g
Carbohydrates: 28g
Fat: 15g
Saturated Fat: 9g
Fiber: 2g
Sugar: 3g
Sodium: 540mg

Frequently Asked Questions

Can I make this soup without dairy?

Yes! Use a plant-based milk like oat or almond, and skip the cheese or use a vegan alternative.

What if my mashed potatoes were already cheesy?

Even better! Just reduce the added cheese in the recipe and taste before adding more.

Can I add meat to this soup?

Absolutely. Cooked bacon, shredded chicken, or ham are great additions.

How do I fix a soup that’s too thick?

Just stir in more broth or milk a little at a time until you reach the desired consistency.

Is this soup gluten-free?

Yes, as long as your mashed potatoes and broth are gluten-free.

Conclusion

Leftover Garlic Mashed Potato Soup is the kind of recipe that proves leftovers can be exciting. It’s easy, fast, and infinitely adaptable, making it perfect for quick lunches or comforting dinners. Whether you stick to the basics or dress it up with cheese and herbs, this soup turns yesterday’s side into today’s star.