French Onion Broccoli Cheese Casserole Recipe

Imagine a warm, comforting casserole that combines the rich flavors of caramelized onions with cheesy broccoli goodness—welcome to the delightful world of the French Onion Broccoli Cheese Casserole Recipe. This dish is a comforting blend of textures and tastes, featuring tender broccoli florets coated in a luscious cheese sauce infused with the classic essence of French onion soup. Topped with crispy fried onions and a buttery breadcrumb crust, this casserole shines as a crowd-pleasing side or a satisfying main. It’s a perfect recipe to bring depth and heartiness to your table while sneaking in some green veggies in a way that everyone will love.

Ingredients You’ll Need

Gathering these straightforward yet flavorful ingredients is the first step toward making magic happen in your kitchen. Each one plays its part: fresh broccoli adds vibrant color and crunch, while the varieties of cheese and caramelized onions create layers of rich, savory depth. Together, they build a casserole you’ll keep coming back to.

• 4 cups fresh broccoli florets: Choose firm, bright green florets for the best texture after blanching.
• 1 large yellow onion: Thinly sliced for slow caramelization, unlocking natural sweetness.
• 2 tbsp unsalted butter (for onions): Helps create that golden, jammy onion goodness without overpowering flavor.
• 1 tbsp olive oil (for onions): Adds a subtle fruitiness and balances the butter’s richness.
• 1 tsp sugar (optional): Assists in caramelizing onions to a perfect deep brown.
• 1/2 tsp salt (for onions): Enhances natural onion sweetness and flavor.
• 1/4 tsp black pepper (for onions): Adds gentle earthiness to the onions.
• 1 tsp fresh thyme leaves or 1/2 tsp dried thyme: Brings a fragrant, herbal note.
• 2 cloves garlic, minced: Adds subtle warmth and depth to the onion mixture.
• 2 tbsp unsalted butter (for sauce): The base for creating a creamy roux in the cheese sauce.
• 2 tbsp all-purpose flour: Thickens the sauce to luscious perfection.
• 1 1/2 cups low-sodium chicken or vegetable broth: Builds a flavorful, savory foundation.
• 1 cup whole milk or half-and-half: Makes the sauce creamy and smooth without heaviness.
• 1 tbsp Dijon mustard: Adds a subtle tang that wakes up the cheese sauce.
• 1 tsp Worcestershire sauce (optional): Imparts umami depth and complexity.
• 1/2 tsp kosher salt (for sauce): Balances sweetness and richness.
• 1/4 tsp black pepper (for sauce): Provides mild heat.
• 1/4 tsp smoked or sweet paprika: Introduces a gentle smoky warmth.
• 1 1/2 cups shredded Gruyère cheese, divided: Offers nutty flavor and melty texture.
• 1 1/2 cups shredded sharp cheddar cheese, divided: Brings boldness and sharpness.
• 1/2 cup finely grated Parmesan cheese, divided: Adds salty, savory umami punch.
• 6 cups lightly crushed French fried onions, divided: Delivers iconic crunch and a little onion kick throughout and on top.
• 1 cup panko breadcrumbs: Used in the topping for extra crispy texture.
• 2 tbsp melted butter (for topping): Helps create a golden, irresistible crust.
• Cooking spray or butter: For greasing the baking dish to prevent sticking.

How to Make French Onion Broccoli Cheese Casserole Recipe

Step 1: Prepare Your Baking Dish and Preheat Oven

Begin by lightly greasing a 9×13-inch baking dish with butter or cooking spray to prevent sticking and set your oven to preheat at 375°F (190°C). This step ensures your casserole bakes evenly and the crispy topping turns perfectly golden.

Step 2: Blanch the Broccoli

Bring a large pot of salted water to a vigorous boil, then drop in the broccoli florets. Boil them just 2 to 3 minutes until they turn bright green and are crisp-tender, locking in color and nutrients. Immediately plunge them into ice water to halt cooking and keep things fresh and vibrant before draining thoroughly and patting dry.

Step 3: Caramelize the Onions

In a large skillet over medium heat, melt 2 tablespoons of butter with one tablespoon olive oil. Add your thinly sliced onions along with 1/2 teaspoon salt and the optional sugar to coax out a deep, sweet caramelization. Let them cook slowly for 20 to 30 minutes, stirring occasionally, until richly golden brown. In the last few minutes, stir in minced garlic and thyme for a fragrant finish before removing from heat.

Step 4: Make the French Onion Cheese Sauce

In a saucepan, melt 2 tablespoons butter and whisk in 2 tablespoons flour to form a smooth, toasty roux. Gradually add broth, stirring to keep it lump-free. Then whisk in milk, Dijon mustard, Worcestershire sauce, salt, pepper, and paprika. Simmer gently until the sauce thickens just enough to coat a spoon. Reduce heat and stir in one cup each of Gruyère and cheddar cheeses plus 1/4 cup Parmesan until melted and silky smooth. Taste and adjust seasoning as needed.

Step 5: Combine Broccoli, Onions, and Sauce

In a large bowl, toss the blanched broccoli together with the fragrant caramelized onions. Pour the warm cheese sauce over and gently fold everything until each bite will be flavorful and cheese-coated. This careful folding keeps the broccoli crisp while fully enveloping it in cheesy richness.

Step 6: Add French Fried Onions Inside the Casserole

For wonderful crunch throughout the casserole, fold in 2 cups of lightly crushed French fried onions into the broccoli cheese mixture before transferring it to your prepared baking dish. This little addition makes every forkful exciting with bursts of crispy onion flavor.

Step 7: Assemble and Top the Casserole

Spread the mixture evenly in your baking dish, then sprinkle the remaining shredded cheeses on top. Mix together 4 cups crushed French fried onions with panko breadcrumbs and melted butter to create that irresistible crispy topping. Spread this over the top evenly.

Step 8: Bake Until Bubbling and Golden

Bake for 20 to 25 minutes, allowing the cheese to melt fully and the topping to turn a deep golden brown. If it browns too quickly, cover loosely with foil toward the end to avoid burning while the casserole finishes cooking.

Step 9: Let It Rest

After baking, let the casserole rest for about 10 minutes to set up slightly. This resting time helps with neat serving and enhances the flavors melding together beautifully in every portion.

How to Serve French Onion Broccoli Cheese Casserole Recipe

Garnishes

Add a sprinkle of fresh chopped parsley or chives over the top for a pop of bright color and fresh herbal notes. A small drizzle of extra melted butter or a few extra crispy fried onions can elevate presentation and add that final touch of indulgence.

Side Dishes

This casserole holds its own wonderfully but pairs beautifully with a crisp green salad dressed with a simple vinaigrette or some buttery crusty bread to mop up every creamy, cheesy bite. For a heartier meal, grilled chicken or roasted pork complements the richness nicely.

Creative Ways to Present

Serve the casserole straight from a rustic cast iron dish for inviting, homestyle charm. Alternatively, portion it into small ramekins for individual servings perfect for dinner parties. You can even spoon it into hollowed-out bell peppers for a fun presentation twist with extra veggie goodness.

Make Ahead and Storage

Storing Leftovers

After cooling the casserole completely, cover it tightly with plastic wrap or transfer to an airtight container. It stores well in the refrigerator for up to 3 days, making it a perfect make-ahead dish for busy weeknights or meal prep.

Freezing

This casserole freezes beautifully. Follow the recipe through assembly but don’t bake it beforehand. Wrap tightly to prevent freezer burn and freeze for up to 2 months. Thaw overnight in the fridge before baking as directed for fresh-from-the-oven goodness any day.

Reheating

To reheat, place portions in an oven-safe dish and warm in a 350°F (175°C) oven for about 15-20 minutes until heated through. To keep the crispy topping from becoming soggy, avoid reheating in the microwave if possible.

FAQs

Can I use frozen broccoli instead of fresh?

Absolutely! Just be sure to thaw and drain the broccoli well to prevent excess moisture, which could make the casserole watery. Fresh broccoli gives the best texture but frozen works fine in a pinch.

Is it possible to make this dish vegetarian?

Yes! Substitute vegetable broth for the chicken broth and omit the Worcestershire sauce if you prefer a strict vegetarian version. The dish will still be rich and flavorful with the cheese and caramelized onions.

Can I use different cheeses?

Definitely try swapping in mozzarella for milder creaminess or fontina for buttery meltiness. However, Gruyère and sharp cheddar together offer a beautiful balance of nuttiness and tang that defines the dish’s signature flavor.

How do I get perfectly caramelized onions?

Patience is key. Cook them slowly over medium to medium-low heat, stirring occasionally. If they get too dark too fast, lower the heat. Adding a pinch of sugar helps accelerate caramelization without burning.

What should I serve this casserole with?

It’s incredibly versatile! Serve it as a side with roasted meats or alongside a fresh salad for a lighter meal. It even works as a vegetarian main with a crusty baguette or garlic bread on the side.

Final Thoughts

If you want to wow your family or guests with a dish that feels cozy, indulgent, and packed with flavor, you really can’t go wrong with this French Onion Broccoli Cheese Casserole Recipe. It’s a delightful marriage of cheesy, savory, crunchy, and fresh that brings all the elements of a fantastic comfort meal. Trust me, once you try making this, it will quickly become a beloved regular in your cooking rotation. Happy baking!

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