Warm Cheesy Skillet French Onion Dip with Crispy Crostini

This warm, cheesy skillet dip takes all the deep, savory flavors of classic French onion soup and turns them into an irresistible party appetizer. Slowly caramelized onions are folded into a creamy blend of cream cheese, sour cream, and Gruyère, then baked until bubbling and golden.

Served with crunchy garlic-rubbed baguette crostini, it's the kind of dip that disappears fast. Whether for game day, a holiday gathering, or a cozy night in, this dish delivers comfort and elegance in every bite.

French onion soup is beloved for its rich, sweet caramelized onions and gooey melted cheese. This dip captures all of that in a shareable, scoopable form. The onions are cooked low and slow with butter, thyme, and a touch of brown sugar until they turn jammy and deeply flavorful.

Then they're folded into a luscious mixture of cream cheese, sour cream, and mayonnaise, layered with nutty Gruyère and Parmesan, and baked until the top is blistered and browned. Serve it hot with crispy crostini for the ultimate crowd-pleasing appetizer.

Ingredients

Why this recipe works

Caramelizing the onions slowly over 30 minutes is the heart of this recipe. Low heat allows the natural sugars in the onions to develop and deepen, creating a sweet, savory base that can't be rushed.

The brown sugar helps coax out even more caramelization, while fresh thyme adds an earthy aromatic note that complements the cheese beautifully.

The combination of cream cheese, sour cream, and mayonnaise creates a rich, creamy base that holds up well to baking without becoming greasy.

Gruyère melts smoothly and adds a nutty flavor, while Parmesan contributes a salty, savory punch. The final bake at high heat ensures the dip is hot all the way through and develops a golden, slightly crisp cheese crust on top.

Notes and substitutions

Use yellow onions for the best balance of sweetness and bite. If you only have white or red onions, they will work, but the flavor will be slightly different. Fresh thyme is important – dried thyme won't provide the same bright, aromatic quality. If you need to substitute, use a pinch of dried thyme, but reduce the amount by half.

For the creamiest result, make sure the cream cheese is fully softened before mixing. A cast iron skillet is ideal for even heating and a beautiful presentation, but any oven-safe skillet or baking dish will work. The crostini can be made ahead and stored in an airtight container for up to 2 days.

• Gruyère cheese: Swiss cheese or Fontina can be used in place of Gruyère for a similar nutty, melty texture.
• Sour cream: Plain Greek yogurt works as a substitute, though it will be slightly tangier and less rich.
• Mayonnaise: Use full-fat plain yogurt or additional sour cream if avoiding mayo, though the dip will be less creamy.
• Baguette: Sourdough or ciabatta slices can replace the baguette for crostini.

Equipment

• Large skillet
• 8-inch cast iron skillet
• Mixing bowl
• Cutting board
• Chef's knife
• Baking sheet
• Pastry brush