Best Yet Onion Soup

This is the bistro-style French onion soup you crave in winter: deeply caramelized onions in a beefy broth, capped with toasted bread and a blistered crown of melted cheese. The use of sweet Vidalia onions gives the broth a fuller, almost honeyed sweetness compared with regular yellow onions.

Get the caramelization right or the soup falls flat. Cook the sliced onions over medium-high heat in butter and olive oil, stirring often, until they’re a warm even brown across the pan. Pale onions equal pale soup.

The sprinkle of flour after caramelizing isn’t optional. It tightens the broth into something with real body that clings to the bread instead of running off in a thin pool.

For the cheese topping, the mix of grated parmesan and shredded mozzarella is what gives the classic stretchy-blistered finish. Parmesan brings the salty savor. Mozzarella does the visual pull. Use the broiler, not a low bake, to char the edges fast while the cheese stays gooey underneath.

Pro Tips

• Slice the onions thin and even. Thick chunks won’t caramelize uniformly.
• Use a heavy-bottomed Dutch oven so the heat distributes evenly and the onions don’t scorch.
• Toast the French bread slices to dry crispness so they float instead of sinking and turning to mush.
• Place the bowls on a sheet pan before broiling. Bubbling cheese will drip and burn onto your oven floor otherwise.

Variations

• Swap mozzarella for traditional gruyere or aged comte for a nuttier, more authentic French finish.
• Splash in ¼ cup of dry white wine or dry sherry after the flour for a deeper, more complex broth.
• Use a mix of yellow and red onions for more visual interest and a slightly sharper finish.