French Onion Sheet Pan Quesadillas

Ingredients needed 

French Onion Beef Filling

• Lean ground beef: Forms the hearty, savory base of the filling, creating a rich and satisfying foundation. I love 90/10 for the best balance of flavor and texture.
• Sweet yellow onions: Slowly caramelized into deep golden, jammy perfection. They’re what make these quesadillas taste like French onion soup.
• Butter and olive oil: The duo that helps the onions caramelize beautifully without burning.
• Garlic: Adds aromatic depth to the beef filling.
• Worcestershire sauce: Brings a savory, umami-rich note that deepens the flavor.
• Fresh thyme: The herb that gives this filling its signature cozy, earthy flavor.
• Kosher salt and black pepper: Balance the sweetness and season the filling.
• Beef broth: Deglazes the pan and adds richness to the beef mixture.
• Dijon mustard: A tangy secret ingredient that brightens the filling.

Quesadillas

• Large burrito-size flour tortillas
• Cheese: This recipe calls for gruyère cheese, low-moisture mozzarella, and sharp white cheddar. 
• Melted butter: Brushed on top for a beautifully golden, crispy crust.

Greek Yogurt French Onion Dipping Sauce

• Plain whole-milk Greek yogurt: Forms the tangy, creamy base of the dip.
• Sour cream: Adds richness and a subtle tang.
• Reserved caramelized onions: Ties the dip to the quesadilla.
• Worcestershire sauce: Enhances the savory depth of the dip.
• Garlic powder and onion powder: Add concentrated flavor without extra prep.
• Fresh chives: Bring a bright, fresh finish.
• Kosher salt and black pepper: Balance the flavors.
• Lemon juice: Adds a bright, tangy finish that balances the richness.

How do you make these French onion quesadillas?

Prepare the caramelized onions:

1. Melt the butter with the olive oil in a large skillet over medium heat. Add the sliced onions and a pinch of salt.
2. Cook for about 20-25 minutes, stirring occasionally, until the onions are very soft, deep golden and caramelized. 
3. Reserve ½ cup of the caramelized onions for the dipping sauce.

PRO TIP: Don’t rush the caramelization of the onions. You want that deep, jammy sweetness throughout the filling.

Make the French onion beef:

1. Push the remaining onions to the edges of the skillet and add the ground beef. Cook, breaking it into small crumbles, until deeply browned.
2. Add the garlic, Worcestershire, Dijon, thyme, salt and pepper.
3. Pour in the beef broth and scrape up all those browned bits from the bottom. Cook for another 2-3 minutes until the liquid has mostly evaporated.

PRO TIP: Let the filling cool for about 10 minutes before assembling the quesadillas. Steaming-hot filling will make soggy tortillas.

Assemble the sheet pan quesadilla:

1. Heat the oven to 425°F and lightly grease an 18×13-inch rimmed half-sheet pan.
2. Lay 6 tortillas around the perimeter of the pan, overlapping them so approximately half of each tortilla hangs over the edge. Make sure the tortillas also overlap each other enough that there aren’t gaps in the bottom.
3. Place 1 tortilla in the center to completely cover the bottom.
4. Sprinkle about half the cheese mixture over the tortillas.
5. Spread the French onion beef mixture evenly over the cheese, then follow with the remaining cheese.
6. Place the last tortilla in the center on top. Fold all of the overhanging tortillas inward over the filling, overlapping them to completely enclose the quesadilla.
7. Brush the top lightly with melted butter.

PRO TIP: Put a second sheet pan directly on top of the quesadilla. This presses everything together and gives you that flat, restaurant-style crispy exterior.

Bake the quesadilla:

1. Bake for 18-20 minutes.
2. Carefully remove the top sheet pan and bake uncovered for another 5-8 minutes, until the tortillas are deeply golden and crisp.
3. Let them rest about 5 minutes before cutting.

Make the Greek yogurt French onion dip:

1. While the quesadilla bakes, finely chop the reserved caramelized onions.
2. Combine all of the French onion dip ingredients.
3. Taste the dip, then adapt as necessary. It should be tangy and savory, because it’s going against a very rich, cheesy quesadilla.
4. Refrigerate the dip until ready to serve.

Serve:

1. Cut the entire sheet-pan quesadilla into 16 squares or rectangles with a large pizza cutter.
2. Pile them onto a big serving board or platter with the Greek yogurt French onion dip right in the middle.
3. Finish the quesadillas with fresh thyme or finely chopped chives. Around the dip, you could add a few simple crunchy things, such as pickles and kettle chips.  

PRO TIP: For a casual dinner, cut them into 8 larger pieces and serve with a green salad.