The onions begin as a crowded pile in the Dutch oven, and for a while it can seem like nothing is happening. Then they soften, shrink, and turn deeply golden as their sweetness builds. I give them the time they need before adding anything else; rushing this part leaves the soup tasting like broth with onions instead of a pot of creamy caramelized onion and potato soup.
Russet potatoes give the finished soup body, while heavy cream rounds out the onion’s sweetness without covering it up. I cut the potatoes into even pieces so they soften at the same pace, then blend the soup until smooth before stirring in the cream. The result is velvety and full-bodied, with the slow-cooked onions doing the work of making each spoonful taste rich.
Kitchen Note
Cut the potatoes into even 1-inch pieces so they become tender together. If a few are much larger, they’ll lag behind while the smaller pieces soften.
Save this creamy caramelized onion and potato soup for a slow-cooked, velvety bowl with deeply golden onions and a smooth finish.
Why These Onions Need Nearly an Hour Before the Potatoes Go In
Three pounds of sliced onions take up a surprising amount of room, and they won’t turn golden just because they’ve softened. They release moisture as they cook; that moisture needs time to evaporate before the onions can deepen in color and sweetness. Keep the Dutch oven over medium-low heat and stir every few minutes, scraping the bottom so nothing catches while the onions slowly reduce.
Adding the potatoes and broth too early changes the job: the onions simmer in liquid instead of cooking down in the butter and oil. Wait until they’re very soft and deeply golden, even if they need the full 65 minutes. The color should be rich and even, not dark brown or scorched. That patient first stage gives the soup its mellow, rounded onion flavor, so the broth and cream don’t have to carry the whole pot.
What the Onions, Russets, and Cream Each Bring to the Pot
- Yellow onions — Their sweetness becomes deeper and more savory as they cook slowly. Choose firm onions without soft spots; there’s no need to seek out a specialty variety. Thin, consistent slices help them soften evenly, and the long cooking time does more for the result than any particular brand.
- Butter and olive oil — Butter brings a rounded, savory base, while the olive oil shares the cooking fat as the onions soften. Use fresh butter and olive oil you like the taste of, but an everyday bottle of olive oil is fine here. The low, steady heat matters more than using a premium oil.
- Russet potatoes — Their starch helps the blended soup feel thick and creamy without relying on cream alone. Choose potatoes that feel firm, peel them, and cut them evenly. Waxy potatoes won’t give the same soft, cohesive texture, so russets are the better choice for this smooth soup.
- Low-sodium broth — This gives the potatoes enough liquid to simmer while leaving room to season the finished soup to taste. Chicken broth makes the base more savory; vegetable broth keeps it vegetarian and has a gentler flavor. Either works, and low-sodium broth gives you more control over the final salt level.
- Heavy cream — Cream gives the blended potatoes a silkier finish and softens the savory edge of the onions. Fresh heavy cream is best for a smooth, rich texture. A thinner dairy swap won’t give quite the same body, so keep the cream if that lush finish is what you’re after.
- Garlic, dried thyme, bay leaf, and black pepper — These season the soup without taking attention away from the onions. Dried thyme is convenient and works well in the brief time it simmers; use a bay leaf that still smells fragrant when you open the jar. Remove the bay leaf before blending so the soup stays smooth.
The Stovetop Sequence That Builds a Smooth, Balanced Soup
Let the Onions Turn Deeply Golden
Melt the butter and olive oil in a 6-quart Dutch oven over medium-low heat, then add the thinly sliced onions and kosher salt. Cook for 50 to 65 minutes, stirring every few minutes, until the onions are very soft and deeply golden brown. They’ll begin crowded and gradually collapse as they release moisture. If the bottom starts to darken before the onions are soft, lower the heat and keep stirring.
Wake Up the Garlic and Thyme
Stir the minced garlic, dried thyme, and black pepper into the golden onions. Cook for 1 minute, just until the garlic smells fragrant. Keep the mixture moving so the garlic doesn’t sit against the hot pot and scorch. It should smell savory and aromatic, not sharp or browned.
Simmer the Potatoes Until They Give Easily
Add the peeled potato pieces, broth, and bay leaf. Bring the pot to a boil over medium-high heat, then reduce the heat to maintain a gentle simmer and cover it. Cook for 20 to 25 minutes, until the potatoes are very tender when pierced. A hard boil can make the pot jostle and break up the potatoes unevenly, so turn the heat down once it reaches a boil.
Blend Smooth, Then Finish Gently With Cream
Remove the bay leaf before blending the soup with an immersion blender until smooth. Keep the blender head submerged to avoid splashing hot soup, and move through the pot until no potato pieces remain. Stir in the heavy cream and warm the soup over low heat for 3 to 5 minutes without letting it boil. Taste and add more salt as needed once the cream is mixed in.
Two Simple Changes for a Different Bowl
Keep It Vegetarian With Vegetable Broth
Use vegetable broth in place of chicken broth for a vegetarian pot. The soup keeps its creamy texture, while the broth gives it a softer, less meaty savoriness.
Leave Some Potato Pieces for a Chunkier Finish
Before blending, scoop out a portion of the tender potatoes and onions. Blend the soup that remains until smooth, then stir the reserved pieces back in for a bowl with soft chunks and a creamy base.
Storage and Reheating
- Refrigerator: Refrigerate in airtight containers within 2 hours; the soup keeps for 3 to 4 days and thickens as it chills.
- Freezer: For the smoothest thawed texture, freeze the blended soup before adding the cream, in airtight containers, for up to 2 to 3 months. Thaw it in the refrigerator, then stir in the cream as you warm it.
- Reheating: Warm gently on the stovetop over low heat, stirring until steaming throughout. Avoid boiling, which can make the cream separate and the texture less silky.
Questions That Come Up With This Onion-and-Potato Soup
Creamy Caramelized Onion and Potato Soup
Ingredients
Equipment
Method
- Melt the unsalted butter and olive oil in a 6-quart Dutch oven over medium-low heat.
- Add the yellow onions and kosher salt and cook for 50 to 65 minutes, stirring every few minutes, until the onions are very soft and deeply golden brown.
- Stir in the garlic, dried thyme, and black pepper and cook for 1 minute, until fragrant.
- Add the russet potatoes, low-sodium chicken or vegetable broth, and bay leaf.
- Bring to a boil over medium-high heat, then reduce the heat to maintain a gentle simmer, cover, and cook for 20 to 25 minutes, until the potatoes are very tender.
- Remove the bay leaf.
- Blend the soup with an immersion blender until smooth.
- Stir in the heavy cream and warm over low heat for 3 to 5 minutes without boiling; taste and add more kosher salt as needed.
