Warm Cheesy Skillet French Onion Dip with Crispy Crostini Tips, FAQ & printable recipe

Tips for success

For the best flavor, use high-quality Gruyère and freshly grate it yourself – pre-shredded cheese often contains anti-caking agents that affect melting. The same goes for Parmesan.

When caramelizing the onions, resist the urge to stir too frequently; letting them sit for a minute or two between stirs helps them develop a deeper color. If the onions stick to the pan, add a splash of water or broth to deglaze, scraping up the browned bits.

To make the crostini extra flavorful, brush them with olive oil and season with a pinch of salt before toasting. The garlic rub is best done while the crostini are still warm from the oven so the garlic infuses into the bread. If you have leftovers, the dip can be reheated in the oven or microwave, but it's best fresh out of the skillet.

Variations

• Bacon French Onion Dip: Cook 4 slices of bacon until crisp, then crumble. Fold half into the dip mixture and sprinkle the rest over the top along with the Gruyère before baking. The smoky, salty bacon adds a delicious savory depth.
• Herb-Infused Version: Add 1 teaspoon of chopped fresh rosemary or sage along with the thyme during caramelization. These herbs complement the onions and cheese beautifully, adding an earthy, aromatic layer.
• Spicy Kick: Stir in 1/2 teaspoon of red pepper flakes or a few dashes of hot sauce into the dip mixture before baking. The heat balances the sweetness of the onions and the richness of the cheese.
• Mushroom & Onion: Sauté 8 oz sliced cremini mushrooms with the onions during the last 10 minutes of caramelization. The mushrooms add an earthy, meaty texture that pairs well with the Gruyère.

Storage and make-ahead

Fridge

Store leftover dip in an airtight container in the refrigerator for up to 4 days. Reheat gently in the oven or microwave before serving.

Freezer

The dip can be frozen for up to 2 months. Thaw overnight in the refrigerator and reheat in the oven at 350°F (175°C) until hot and bubbly.

Reheat

Reheat leftover dip in a 350°F (175°C) oven for 10-15 minutes, or in the microwave in 30-second bursts, stirring between, until hot.

Store any leftover dip in an airtight container in the refrigerator for up to 4 days. The crostini should be stored separately in a sealed bag at room temperature for up to 2 days.

To reheat the dip, place it in an oven-safe dish and warm at 350°F (175°C) for 10-15 minutes, or until hot and bubbly. Avoid microwaving the crostini, as they will become soggy – reheat them in the oven or toaster if needed.

The caramelized onions can be made up to 3 days ahead and stored in the refrigerator. The dip can be fully assembled (without the top cheese) up to 24 hours in advance and kept covered in the fridge.

When ready to bake, sprinkle the remaining Gruyère over the top and bake as directed, adding 5-10 minutes to the baking time if the dip is cold from the fridge.

Serving ideas

Serve the dip warm, straight from the skillet, with a generous pile of toasted crostini on the side. The contrast between the hot, creamy dip and the crunchy, garlicky bread is irresistible.

For a party, set the skillet on a trivet and let guests help themselves. The dip is also delicious with crudités like carrot sticks, celery, or bell pepper slices for a lighter option.

For a more substantial appetizer, serve the dip with additional baguette slices or even warm pita chips. The dip pairs well with a crisp white wine like Sauvignon Blanc or a light beer. If you have any leftover dip, it's fantastic as a spread for burgers or sandwiches the next day – just warm it slightly to make it spreadable.

Frequently asked questions

Recipe card

Warm Cheesy Skillet French Onion Dip with Crispy Crostini

Prep 15 minCook 50 minTotal 1 h 5 minServes 8

Ingredients

• 3 large yellow onions, thinly sliced
• 2 tbsp unsalted butter
• 1 tbsp olive oil
• 1 tsp brown sugar
• 1 tbsp fresh thyme leaves, plus more for garnish
• 200 g cream cheese, softened
• 1/2 cup sour cream
• 1/4 cup mayonnaise
• 1 cup shredded Gruyère cheese
• 1/4 cup grated Parmesan cheese
• 1/2 cup shredded Gruyère cheese, for topping
• 1 baguette, sliced into 1/2-inch rounds
• 1 clove garlic, halved
• 2 tbsp olive oil, for brushing

Instructions

1. Heat the butter and olive oil in a large skillet over medium heat. Add the sliced onions, brown sugar, and fresh thyme. Cook slowly, stirring occasionally, for about 30 minutes until the onions are deeply golden, jammy, and sweet. Reduce heat if they begin to brown too quickly.
2. Remove the skillet from the heat and let the onions cool for about 5 minutes. This prevents the hot onions from melting the cream cheese too quickly when combined.
3. In a mixing bowl, combine the softened cream cheese, sour cream, and mayonnaise. Stir until smooth and well blended. Add the shredded Gruyère and grated Parmesan, then fold in the cooled caramelized onions.
4. Spread the dip mixture evenly into an 8-inch cast iron skillet. Smooth the top with a spatula. Sprinkle the remaining 1/2 cup shredded Gruyère over the top, covering the surface completely.
5. Preheat the oven to 375°F (190°C). Place the skillet in the oven and bake for 20 minutes, until the dip is hot and bubbling and the top is golden brown with browned cheese blisters.
6. While the dip bakes, arrange the baguette slices on a baking sheet. Brush both sides lightly with olive oil. Toast in the oven for 5-7 minutes, flipping once, until golden and crisp. Rub each warm crostini with the cut side of the garlic clove.
7. Remove the dip from the oven and let it cool for a few minutes. Garnish with fresh thyme leaves. Serve warm with the toasted baguette crostini for dipping.

Contains: gluten, milk, eggs

Estimated nutrition per serving

Calories

380

Protein

12 g

Carbohydrates

22 g

Fat

27 g

Automatic estimate from the ingredient list, not laboratory-verified.