Description
A savory and delicious side dish made with sweet onions, broth, and two types of cheese, inspired by the flavors of French onion soup. Perfect as a crowd-pleasing appetizer or side for any meal.
Ingredients
Units
Scale
Main Ingredients
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- 2 tablespoons extra-virgin olive oil
- 2 tablespoons unsalted butter, melted, divided
- 1 tablespoon plus 1/2 teaspoon chopped fresh thyme, divided, plus leaves for garnish
- 1/2 teaspoon salt
- 1/2 teaspoon ground pepper
- 3 large sweet onions (12 oz. each), peeled and sliced 1-inch thick
Topping
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- 1/3 cup panko breadcrumbs
- 1/2 cup shredded Gruyère cheese
- 1/2 cup shredded low-moisture part-skim mozzarella cheese
Roasting Liquid
- 1/2 cup lower-sodium beef broth
- 1 tablespoon sherry vinegar
Instructions
- Preheat the oven: Position the oven rack in the upper third of the oven and preheat to 450°F.
- Prepare the butter mixture and onions: Whisk together the olive oil, 1 tablespoon melted butter, 1 tablespoon thyme, and ½ teaspoon each salt and pepper in a small bowl. Arrange the onion slices in a single layer in a broiler-safe metal baking pan (avoid glass or ceramic). Brush the butter mixture all over the onions. Do not wipe out the bowl; set it aside. Roast the onions in the oven, flipping once halfway, until lightly browned on both sides, about 30 minutes.
- Prepare the panko breadcrumbs: Combine the remaining 1 tablespoon melted butter, ½ teaspoon thyme, and panko breadcrumbs in the reserved bowl. Transfer the mixture to a nonstick skillet and cook over medium-high heat, stirring occasionally, until golden brown and fragrant, 2 to 3 minutes. Remove from heat and let cool.
- Add broth and vinegar to the onions: Flip the onions once more in the baking pan. Carefully pour ½ cup broth and 1 tablespoon sherry vinegar into the pan. Return the pan to the oven and roast until the broth is slightly reduced and the onions are very soft, about 10 minutes more.
- Broil with cheese: Set the oven to broil and combine the shredded Gruyère and mozzarella cheeses. Evenly sprinkle the cheese mixture over the onions. Broil until the cheese is melted and bubbling, about 1 minute.
- Add the panko topping and serve: Sprinkle the reserved toasted panko over the top of the onions. Garnish with fresh thyme leaves if desired. Serve immediately, including any sauce left in the pan.
Notes
- Ensure you use a metal baking pan, as glass or ceramic pans may shatter when using high oven temperatures.
- For a vegetarian version, replace beef broth with vegetable broth.
- Serve as a side dish or as a unique appetizer with crusty bread.
- The panko topping can be made ahead and stored at room temperature for up to one day.
Nutrition
- Serving Size: 1 serving
- Calories: 150
- Sugar: 4g
- Sodium: 230mg
- Fat: 10g
- Saturated Fat: 5g
- Unsaturated Fat: 4g
- Trans Fat: 0g
- Carbohydrates: 10g
- Fiber: 1g
- Protein: 5g
- Cholesterol: 20mg
