How To Make Costco's Frozen French Onion Soup Taste Homemade
French onion soup is rich, comforting, simple, and timeless. It also takes about two hours to make, with at least 90 minutes of that time being active, hands-on cooking. If you have time to make it, there's something meditative about the stirring of onions until their sweetness is coaxed out, something healing about feeding them sherry and bathing them in stock, adorning them with a coat of cheese and bronzing them in the oven with a blanket of bread. It reminds us that something so simple and so taken for granted is worthy of care — and can become magical.
But if you don't have that kind of time (who does?) and want some delicious, homemade French onion soup (who doesn't?), there's another way. In the freezers at Costco, there's an $11 cheat code: 3.7 pounds of frozen French onion soup — in six individual portions — ready in as little as 5 minutes. No onion tears required.
To make it taste more homemade, we have some easy tips gleaned from Laura Manzano of The Kitchn. Thicken the soup with a cornstarch slurry, add more cheese, and top it with toasted bread.
Zhuzhing up Costco soup in three easy steps
Laura Manzano of The Kitchn recommends three updates to bring Costco's frozen soup to life. Finding the soup a bit thin, she thickens it up with a cornstarch slurry. Could you use flour? Sure, if you're heating the soup on the stove and willing to cook it a little longer. If you're heating the soup in the microwave, cornstarch won't leave your soup tasting like raw flour. Unless you're aiming for a French onion stew, don't overdo it. If you're making all 6 portions, 1 tablespoon of cornstarch to 1 cup of water will do. For a single portion, ½ teaspoon cornstarch to 2½ tablespoons water will do.
Next comes the cheese and bread. The frozen soup comes with both, but Manzano found them lacking. The croutons in the frozen soup are soggy upon reheating; it's best to replace this with thick slices of toasted, crusty buttered bread. Top the soup with a slice and a generous shower of grated gruyere and parm.
One of the best things about French onion soup is that it's another socially acceptable vehicle for shoveling spoonfuls of melted cheese and bread into your mouth. There's never enough. While you're at it, crack some fresh black pepper in there to freshen the spice.
Or get a little extra
To take it even further, we have a couple of extra tricks. Basically, we'll be combining some of the steps of a great homemade French onion soup with the Costco frozen soup as a shortcut. It can be refrozen at home without the extra cheese and bread, so go ahead and make the whole batch.
Hack one: Swap the cornstarch slurry for a proper butter and flour roux. This will add richness and body to the soup. Cook flour in butter long enough for it to start going golden but not long enough for it to brown to cook off the floury taste.
Hack two: Add depth of flavor. Costco's French onion soup is a vegetable stock base and has no booze in it. A traditional recipe employs sherry and either chicken or beef stock. Anthony Bourdain's used balsamic vinegar and port. A touch of bouillon and a splash of sherry (cooking or drinking) or port and a drizzle of balsamic will create levels in your frozen soup without watering it down.
Hack three: When it comes to the toast, why wouldn't you make it garlic toast? Toast that bread with some butter or olive oil, then rub a little peeled clove of garlic over it. It'll elevate the cheese as it melts over the toast and those cheesy oils mingle with the garlic. Thank us later.