Ingredients

- 8 +

• 6 large sweet onions, thinly sliced into uniform rings for even cooking
• 1/3 cup premium honey, preferably local wildflower variety for best flavor
• 1/4 cup Dijon mustard, smooth and creamy variety
• 2 tablespoons whole grain mustard for added texture and visual appeal
• 3 cups vegetable or chicken broth, preferably low-sodium
• 2 cups heavy cream, brought to room temperature
• 2 cups shredded Gruyere cheese, divided for layering
• 1 cup seasoned breadcrumbs for a crispy golden topping
• 4 tablespoons unsalted butter, divided for sauting and topping
• 3 cloves garlic, finely minced for aromatic depth
• 2 tablespoons fresh thyme leaves, stripped from stems
• 1 tablespoon Worcestershire sauce for umami enhancement
• 1 teaspoon sea salt, or to taste
• 1/2 teaspoon freshly ground black pepper

Instructions

1

Preheat your oven to 375F (190C) and position the rack in the center for optimal heat distribution

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2

In a large skillet over medium heat, melt 2 tablespoons butter until foamy and add the sliced onions

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3

Cook onions for 25-30 minutes, stirring occasionally, until deeply caramelized and golden brown

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4

Add minced garlic and fresh thyme to the onions during the last 5 minutes of caramelizing

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5

In a medium bowl, whisk together honey, both mustards, Worcestershire sauce, salt, and pepper until well combined

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6

Pour the honey-mustard mixture over the caramelized onions and stir to coat evenly

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7

Transfer the onion mixture to a greased 9x13 inch casserole dish and spread in an even layer

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8

Pour the heavy cream over the onions and sprinkle with 1 cup of the Gruyere cheese

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9

In a small bowl, mix breadcrumbs with remaining melted butter and remaining cheese

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10

Sprinkle the breadcrumb mixture evenly over the top of the casserole

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11

Bake for 45-55 minutes until golden brown and bubbling around the edges

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12

Let rest for 10-15 minutes before serving to allow the sauce to thicken properly

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Kitchen Tools

• Large heavy-bottomed skillet or saut pan for caramelizing onions
• 9x13 inch ceramic or glass baking dish
• Sharp chef's knife for uniform onion slicing
• Sturdy wooden spoon or silicone spatula for stirring

Chef's Tips

Choose sweet onions like Vidalia or Walla Walla for the most delicate and naturally sweet flavor profile

Take your time caramelizing the onions - rushing this step will result in less developed flavors

Use room temperature ingredients to ensure even cooking and prevent the cream from curdling

For extra depth of flavor, deglaze the pan with a splash of white wine after caramelizing the onions

🔧 Troubleshooting Tips

️

If sauce is too thin, continue baking uncovered for an additional 5-10 minutes

️

If top browns too quickly, cover with foil for the remainder of cooking time

️

If onions are burning while caramelizing, lower heat and add a splash of water

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If mixture seems dry, add additional broth 1/4 cup at a time

🔄 Recipe Variations

Add crumbled bacon or pancetta for a smoky meat-lovers version

Incorporate sauted mushrooms for an earthier vegetarian option

Include caramelized shallots and leeks for a more complex allium flavor

Top with crispy fried onions instead of breadcrumbs for extra crunch

🥗 Healthy Alternatives

Substitute heavy cream with unsweetened cashew cream or light coconut milk for a lighter version

Use whole wheat panko breadcrumbs instead of regular breadcrumbs for added fiber

Replace half the cheese with nutritional yeast for a lower-fat option with similar flavor

Use sugar-free honey substitute and reduced-sodium broth for a more diet-friendly version

🍽️ Serving Suggestions

Serve alongside herb-crusted roasted chicken for an elegant main course combination

Pair with a light arugula salad dressed with lemon vinaigrette to balance the rich flavors

Offer crusty whole grain bread on the side to soak up the delicious sauce

Garnish with additional fresh thyme sprigs and a drizzle of honey for presentation

Nutrition Facts

385

Calories

12g

Protein

32g

Carbs

24g

Fat

🥗 Suitable Diets

Can be adapted for gluten-free diets by using gluten-free breadcrumbs

Suitable for vegetarian diets when made with vegetable broth

Can be modified for dairy-free diets using non-dairy alternatives

Not suitable for vegan diets without significant modifications

🎨 Presentation Ideas

Fresh thyme sprigs for elegant presentation

Drizzle of honey and whole grain mustard

Crispy fried onion bits for textural contrast

Chopped fresh parsley for color and freshness

📦 Storage & Conservation

Store leftovers in an airtight container in the refrigerator for up to 3 days

Freeze portions in freezer-safe containers for up to 2 months

Thaw frozen portions overnight in the refrigerator before reheating

Reheat covered in a 350F oven until warmed through, about 20 minutes

♻️ Leftover Ideas

Use as a savory topping for grilled steaks or chicken

Incorporate into quiche or frittata for breakfast

Blend with stock for a creamy onion soup base

Spread on toasted baguette slices for a unique crostini

⚠️ Common Mistakes to Avoid

Rushing the onion caramelization process, which prevents proper flavor development

Using cold dairy ingredients that can cause separation and uneven cooking

Overcrowding the pan while caramelizing onions, which leads to steaming instead of browning

Not allowing adequate resting time before serving, resulting in runny sauce

FAQ

Can I make this ahead of time? ▶

Yes, you can assemble up to 24 hours in advance and bake just before serving

What type of onions work best? ▶

Sweet onions like Vidalia are ideal, but any yellow or white onions will work

Can I freeze this casserole? ▶

Yes, but the texture may change slightly upon thawing

How do I prevent the top from burning? ▶

Cover with foil if it browns too quickly while baking

Can I use dried herbs instead of fresh? ▶

Yes, but use only 1 teaspoon of dried thyme as it's more concentrated

Reviews

Sarah M.

⭐⭐⭐⭐⭐

Feb 10, 2026

This casserole is absolutely divine! The honey mustard glaze takes it to another level.

Michael P.

⭐⭐⭐⭐☆

Feb 6, 2026

Delicious comfort food that's perfect for fall gatherings.

Emma R.

⭐⭐⭐⭐⭐

Jan 24, 2026

The caramelized onions make this dish incredibly special.

James T.

⭐⭐⭐☆☆

Feb 10, 2026

Good flavor but took longer to prepare than expected.

Linda K.

⭐⭐⭐⭐⭐

Jan 16, 2026

My new favorite side dish! Everyone asks for the recipe.