Chicken broccoli casserole with cheddar and mushroom sauce

There’s nothing like a pan of bubbling casserole to make a house feel like home. I love this chicken broccoli casserole because it smells like Sunday mornings and warm hugs — the mushrooms release that savoury, earthy perfume, the cheddar melts into glossy ribbons, and the top gets those crispy golden edges that make everyone pause mid-conversation. When I toss this together, I picture my kitchen full of chatter, a spoon clinking against the baking dish, and the oven door opening to that irresistible steam. It’s cozy, forgiving, and exactly the kind of food I reach for when I want comfort without fuss.

Quick Facts

• Yield: Serves 6
• Prep Time: 20 minutes
• Cook Time: 35 minutes
• Total Time: 55 minutes

Why This Recipe is Awesome

This casserole hits all the home-cook marks: creamy, cheesy sauce; tender chicken; bright green broccoli; and a toasty, crunchy top. It’s comfort-food with a bit of lift — the mushrooms add earthiness, cheddar brings depth, and breadcrumbs add satisfying crunch. It’s so easy even your oven can’t mess it up. Who doesn’t love that warm, bubbling surface and the first spoonful that strings gooey cheese between plate and baking dish?

Ingredients

For the Main Dish:

• 3 cups cooked chicken, shredded or diced (about 1.5 lb raw before cooking)
• 4 cups fresh broccoli florets (or 12 oz frozen, thawed)
• 8 oz white or cremini mushrooms, sliced
• 1 medium yellow onion, finely chopped (about 1 cup)
• 2 cloves garlic, minced
• 3 tbsp unsalted butter
• 3 tbsp all-purpose flour
• 2 cups whole milk
• 1/2 cup low-sodium chicken broth
• 2 cups shredded sharp cheddar cheese, divided
• 1 tsp Dijon mustard (optional)
• 1/2 tsp smoked paprika
• Salt and freshly ground black pepper, to taste
• 2 tbsp olive oil (for sautéing)

For the Sauce / Garnish (if applicable):

• 3/4 cup breadcrumbs or crushed buttery crackers
• 2 tbsp melted butter (for topping)
• 2 tbsp chopped fresh parsley or chives for garnish

How I Make It

Step 1:

Preheat your oven to 375°F. I start by sautéing the aromatics: heat 2 tbsp olive oil in a large skillet over medium-high heat. Add the onion and cook until it turns translucent and smells sweet, about 3–4 minutes. Toss in the mushrooms and sauté until they release their juices and turn golden, another 4–5 minutes. Stir in the garlic for 30 seconds until fragrant.

Step 2:

Turn the heat to medium and melt 3 tbsp butter in the pan. Sprinkle in 3 tbsp flour and whisk constantly for about 1 minute to cook out the raw flavor. Slowly whisk in 2 cups milk and 1/2 cup chicken broth, scraping any browned bits. The sauce will thicken as it heats — that’s when the smell changes and you know you’re on the right track.

Step 3:

Reduce heat to low and stir in 1 1/2 cups cheddar (reserve the rest for topping), 1 tsp Dijon, smoked paprika, and a pinch of salt and pepper. The sauce should become glossy and cling to the back of a spoon. Fold in the cooked chicken and broccoli until everything looks evenly coated and puckered with cheesy goodness.

Step 4:

Pour the mixture into a greased 9×13-inch baking dish. Mix the breadcrumbs with 2 tbsp melted butter and sprinkle over the top along with the remaining 1/2 cup cheddar. Bake uncovered for 20–25 minutes until the top turns golden and the edges bubble. If you want extra color, broil for the last 1–2 minutes while watching closely so it doesn’t burn.

Step 5:

Let the casserole rest for 5–10 minutes before serving so the sauce sets a little and you don’t steam your tongue off. Sprinkle with chopped parsley or chives for a fresh, green pop. The texture should be creamy inside with a crisp, toasty topping and pockets of browned cheese around the edges.

Pro Tips

• Use day-old breadcrumbs or crushed crackers for a crunchier topping — they toast better than fresh crumbs.
• If your sauce gets too thick, whisk in a splash of milk or chicken broth to loosen it; if it’s thin, simmer a few minutes to reduce.
• For extra flavor, roast the broccoli at 425°F for 8–10 minutes before adding — it adds smoky char and keeps it from getting mushy.
• Cook chicken ahead and shred while warm; it soaks up flavor better than cold chicken straight from the fridge.

Common Mistakes to Avoid

• Skipping preheating: Classic rookie move. It changes texture and bake time.
• Overmixing: Leads to dense or chewy results. Mix until just combined.
• Guessing cook time: Always use visual cues or a timer, not just vibes.
• Overcrowding pans: Give your food some breathing room to crisp properly.

Alternatives & Substitutions

• Swap chicken for firm tofu (press and cube) to make it vegetarian; this reduces richness slightly but keeps protein. Add sautéed spinach for color.
• Use Greek yogurt in place of half the milk for tang and a bit more protein; it will make the sauce thicker and tangier.
• For a dairy-free version, use unsweetened oat milk plus a dairy-free cheddar-style shreds and a plant-based butter substitute.
• Gluten-free? Use a 1-to-1 GF flour in the sauce and GF breadcrumbs or crushed rice crackers for the topping.

Variations & Tips

• Spicy: Stir in 1 tsp chili flakes or a diced jalapeño with the onions for a kick.
• Kid-friendly: Omit mushrooms and add diced carrots or corn for familiar flavors.
• Low-carb: Skip breadcrumbs; top with crushed pork rinds or sliced almonds for crunch.
• Mediterranean twist: Swap cheddar for feta and add sun-dried tomatoes and olives.
• Comfort upgrade: Stir in 4 oz cream cheese with the sauce for extra silkiness.
• Creative twist: Add 1/2 cup cooked wild rice to the filling for nutty texture and bulk.

FAQ (Frequently Asked Questions)

Can I make this ahead of time?

Yes! Assemble the casserole, cover tightly, and refrigerate up to 24 hours. Add 5–10 extra minutes to the bake time if baking straight from cold. For best texture, let it sit at room temperature for 20 minutes before baking.

Can I double the recipe?

Sure thing. Use a 9×13 and a second 9×13, or a larger pan. Bake time may increase by 5–10 minutes — watch for bubbling edges and a golden top.

Can I substitute butter with oil?

Technically yes, but you’ll miss that buttery magic. Use ¾ the amount of oil.

How do I know it’s done?

Look for bubbling sauce around the edges, a golden-brown topping, and cheese that has melted into glossy pools. The internal temperature of the chicken filling should be at least 165°F if you want to verify.

What if I don’t have ingredient X?

No drama — swap mushrooms for canned, drained artichoke hearts or extra onions. If you lack cheddar, use Monterey Jack or Colby for similar melt and flavor.

How I Like to Serve It

I serve this casserole with a crisp green salad dressed in lemon vinaigrette to cut through the richness and a glass of chilled white wine — sauvignon blanc or unoaked chardonnay work great. For weeknights, pair it with garlic bread and a simple slaw. It also travels well to potlucks; bring it in the baking dish and reheat at 350°F for 15–20 minutes.

Notes

• Store leftovers covered in the fridge for up to 3 days. Reheat in a 350°F oven until warmed through to keep the topping crisp.
• Safe cooking temp for chicken: 165°F. Use an instant-read thermometer if unsure.

Final Thoughts

Closing: Now go impress someone — or just yourself — with this warm, cheesy, mushroomy chicken broccoli casserole!