Can I use yellow or red onions instead of sweet onions?

Absolutely! Yellow onions will give the dish a slightly stronger, more classic onion flavor, while red onions add a bit of color and a slightly sharper taste. Just keep the slices thick and the roasting time about the same.

What’s the best way to avoid soggy panko topping?

Make sure to toast the panko until golden and crispy before topping the onions. Always add the crumb mixture after broiling, not before, so it stays perfectly crunchy.

Can I make this dish vegetarian or even vegan?

Yes on both! Replace beef broth with a robust vegetable broth and use plant-based butter and cheeses. Look for vegan Gruyère-style cheese and mozzarella—several brands melt beautifully now.

My onions aren’t softening enough—what can I do?

If the onions aren’t meltingly soft after the suggested roasting time, simply add a bit more broth and continue roasting until they're collapsed and luscious. Oven temperatures can vary, so let visual cues guide you.

French Onion Soup-Style Melting Onions Recipe

Description

Experience the classic flavors of French onion soup in an easy, casserole-style side dish. Sweet onions are roasted until tender, topped with gooey melted Gruyère and mozzarella, and finished with crispy, buttery panko for irresistible texture. Perfect for a cozy dinner or to elevate your favorite main courses, this recipe captures all the savory, cheesy goodness without the fuss of soup.

Ingredients

Units Scale

For the Onions

3 large sweet onions (12 oz. each), peeled and sliced 1-inch thick

For the Butter Mixture

2 tablespoons extra-virgin olive oil
2 tablespoons unsalted butter, melted, divided
1 tablespoon plus 1/2 teaspoon chopped fresh thyme, divided, plus extra leaves for garnish
1/2 teaspoon salt
1/2 teaspoon ground pepper

For the Crispy Topping

1/3 cup panko breadcrumbs

For Baking and Finishing

1/2 cup lower-sodium beef broth
1 tablespoon sherry vinegar
1/2 cup shredded Gruyère cheese
1/2 cup shredded low-moisture part-skim mozzarella cheese

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Instructions

Prepare Oven and Pan: Position an oven rack in the upper third and preheat the oven to 450°F. Use a 9-by-13-inch metal baking pan; avoid glass or ceramic pans as they may shatter with high heat.
Make the Butter Mixture: In a small bowl, whisk together 2 tablespoons olive oil, 1 tablespoon melted butter, 1 tablespoon thyme, salt, and pepper.
Arrange and Season Onions: Place the onion slices in an even layer in the prepared baking pan. Brush them thoroughly with the butter mixture. Do not clean the bowl, as it will be used in the next step.
Roast the Onions: Roast the onions in the preheated oven, flipping once halfway through, until both sides are lightly browned, about 30 minutes total.
Prepare the Panko Topping: While the onions roast, add the panko breadcrumbs, remaining 1 tablespoon melted butter, and ½ teaspoon thyme to the reserved butter mixture bowl. Toss until the panko is evenly coated. Transfer the mixture to a small nonstick skillet and cook over medium-high heat, stirring occasionally, until golden brown and fragrant, about 2–3 minutes. Remove from heat and set aside to cool.
Add Broth and Vinegar: Flip the roasted onions once more. Carefully pour ½ cup beef broth and 1 tablespoon sherry vinegar into the pan with the onions.
Roast to Finish: Return the pan to the oven and roast until the broth is slightly reduced and the onions are very soft, about 10 minutes more. Remove from the oven.
Add Cheese and Broil: Increase the oven temperature to broil. In a small bowl, combine the Gruyère and mozzarella cheeses, then sprinkle evenly over the onions. Broil until the cheese melts and bubbles, about 1 minute.
Finish and Garnish: Sprinkle the cooled panko mixture on top of the melted cheese. Garnish with extra thyme leaves, if desired, and serve immediately with any sauce left in the baking pan.

Notes

Use metal pans only—glass and ceramic can shatter at this oven temperature.
Shred the cheese yourself for best melting results.
For extra flavor, add a splash more sherry vinegar just before serving.
This dish is best served hot and fresh, but leftovers can be reheated gently in the oven.

Nutrition

Serving Size: 1/8 of recipe
Calories: 180
Sugar: 6g
Sodium: 350mg
Fat: 11g
Saturated Fat: 5g
Unsaturated Fat: 5g
Trans Fat: 0g
Carbohydrates: 14g
Fiber: 2g
Protein: 6g
Cholesterol: 20mg