Buttery Onion Soup

This isn’t classic French onion soup. There’s no broiler, no baguette raft, no Gruyere crown. What you get instead is a creamy, cheesy onion soup that drinks like a chowder and comes together on a weeknight without any of the bistro fuss.

The move that makes this work is patience with the onions. A full 20 to 30 minutes of low and slow sauteing in margarine is what coaxes out the natural sweetness. Rush it on high heat and you’ll get sharp, undercooked onion bite instead of that mellow, almost candy-like depth.

The flour gets sprinkled directly onto the cooked onions to form a roux in the pan. This is what thickens the soup into something silky rather than thin and brothy. Stir it well and let it cook for a minute before adding liquid or you’ll end up with raw flour taste.

Mozzarella is the unconventional choice. Most onion soups use sharper aged cheeses, but mozzarella gives this version that creamy, ropy stretch and a milder flavor that lets the onions stay center stage. Add it at the very end and stir constantly. Boiling will break the cheese into a stringy oily mess.

Pro Tips

• Use a heavy-bottomed pot. Aluminum or thin pans cause hot spots that scorch the onions before they sweeten.
• Slice the onions thinly and uniformly so they cook at the same rate. A mandoline helps.
• Top with croutons and an extra sprinkle of cheese for a quick gratin under the broiler.
• Add a splash of dry white wine after the onions soften for a brighter, more layered flavor.

Variations

• Use butter instead of margarine for richer flavor (the dish is named for the buttery profile).
• Swap mozzarella for half Gruyere and half Swiss for a French onion lean.
• Add 1 teaspoon of fresh thyme leaves with the broth for an herbal upgrade.