Substitutions

• Swiss cheese for Gruyère: Swiss cheese is usually easier on the grocery budget and still gives you a mild nutty character that fits the French onion theme.
• Provolone for some or all of the Gruyère: Provolone melts beautifully and gives the soup a slightly milder cheese flavor.
• Half and half for heavy cream: Half and half makes the soup a little lighter while still adding plenty of creaminess.
• Plain Greek yogurt for sour cream: Greek yogurt gives you a similar tang and creamy texture, though I would use full fat yogurt when possible for the smoothest finish.
• Chicken broth for beef broth: Chicken broth works well if that is what you have, but the finished soup will have a lighter savory flavor.
• Seasoned croutons for garlic croutons: Any sturdy seasoned crouton can add the crunchy bread element if garlic croutons are not available.

Variations

• Crispy Onion French Onion Potato Soup: Skip the croutons and scatter crispy fried onions over each bowl for even more onion flavor and a salty crunch.
• Three Cheese French Onion Potato Soup: Use a combination of Gruyère, Swiss, and provolone for a richer cheese pull and a more layered flavor.
• Loaded French Onion Potato Soup: Top each bowl with bacon, extra cheese, sour cream, crispy onions, and sliced green onions for a mashup of loaded baked potato soup and French onion soup.
• Extra Herb Soup: Add a little fresh thyme at the end along with parsley to brighten the rich broth and creamy cheese.
• Thinner Bistro Style Soup: Stir in additional warm beef broth until the soup reaches a looser consistency, then serve it with extra croutons for soaking.

Tips and Tricks

• Peel the potatoes completely: Removing all the skin gives the soup a smoother texture and keeps the creamy broth looking lighter.
• Stick with russet potatoes when possible: Their higher starch content is exactly what you want because it naturally helps thicken the soup as the potatoes cook and mash.
• Leave plenty of potato chunks: Mash only enough potatoes to create body in the broth so every bowl still has satisfying tender pieces.
• Adjust the thickness with warm broth: Potato soup continues to thicken as it sits, so a splash of warm beef broth can quickly loosen it if needed.
• Add dairy near the end: Heavy cream, sour cream, and cheese stay smoother when they are added after the long cooking period.
• Keep the final heat gentle: Boiling a cheese based soup can cause the cheese and dairy to separate or become grainy.
• Shred the cheese yourself: Prepackaged shredded cheese often contains coatings that keep the strands separate in the bag, and those coatings can prevent smooth melting.
• Taste before adding more salt: The condensed soup, beef broth, Worcestershire sauce, and Gruyère already bring quite a bit of saltiness to the pot.
• Add croutons right before serving: They are at their best when the bottoms soak up a little creamy broth while the tops stay crisp.

Serving Ideas

• Warm crusty bread: A thick slice of bread is great for swiping through the last spoonfuls of creamy onion broth at the bottom of the bowl.
• Simple green salad: Crisp lettuce with a bright vinaigrette balances the richness of the potatoes, cream, and cheese.
• Roasted green beans: Their slightly crisp texture gives you a nice contrast beside a bowl of soft, creamy soup.
• Roasted broccoli: Broccoli is easy, family friendly, and sturdy enough to stand up to the rich Gruyère and beef broth flavors.
• Turkey or ham sandwiches: A simple sandwich turns a bowl of soup into a filling dinner for especially hungry kids or adults.
• Extra toppings on the table: Set out additional croutons, shredded cheese, chopped herbs, crispy onions, or green onions and let everybody finish their own bowl.

Storage and Make Ahead Tips

• Refrigerate leftovers for up to 4 days: Let the soup cool, transfer it to an airtight container, and keep it refrigerated until you are ready to reheat it.
• Expect the soup to thicken overnight: The russet potatoes will continue absorbing liquid, so yesterday's soup may look considerably thicker when you pull it from the refrigerator.
• Loosen leftovers while reheating: Add a splash of beef broth, milk, or heavy cream and stir until the soup returns to the consistency you like.
• Reheat gently on the stove: Use medium low heat and stir regularly until the soup is hot, taking care not to let it boil.
• Microwave individual servings carefully: Heat one bowl at a time in short intervals, stirring between rounds so the creamy soup warms evenly.
• Prepare the base ahead for freezing: Cook the potatoes, onion, garlic, broth, soup, seasonings, and butter, then cool and freeze that base before the dairy and cheese are added.
• Add toppings only when serving: Store croutons separately so they stay crisp, and add the extra Gruyère and fresh herbs after the soup has been reheated.