Prep Time: 20 minutes
Cook Time: 55 minutes
Total Time: 1 hour 15 minutes
Servings: 6

Ingredients

For the Spaghetti Squash

• 1 large spaghetti squash (3–4 pounds)
• 2 tablespoons olive oil
• 1 teaspoon salt
• ½ teaspoon black pepper

For the Broccoli

• 3 cups broccoli florets, cut into bite-sized pieces
• ½ teaspoon salt
• Water for blanching

For the Cheese Sauce

• 3 tablespoons butter
• 3 cloves garlic, minced
• 1 small onion, finely diced
• 3 tablespoons all-purpose flour
• 2 cups whole milk
• ½ cup heavy cream
• 2 teaspoons Dijon mustard
• ½ teaspoon smoked paprika
• ¼ teaspoon cayenne pepper (optional)
• ½ teaspoon garlic powder
• ½ teaspoon onion powder
• ½ teaspoon black pepper
• 1 teaspoon salt (or to taste)
• 2½ cups freshly shredded sharp cheddar cheese
• ½ cup mozzarella cheese
• ¼ cup grated Parmesan cheese

For the Topping

• ½ cup panko breadcrumbs
• ¼ cup grated Parmesan cheese
• 1 tablespoon melted butter
• 1 tablespoon chopped fresh parsley

Optional Add-Ins

• 1 cup cooked shredded chicken
• 6 slices cooked bacon, crumbled
• ½ teaspoon red pepper flakes
• Fresh thyme leaves
• Chopped chives

Equipment Needed

• Sharp knife
• Baking sheet
• Large skillet
• Saucepan
• Mixing bowl
• 9×13-inch baking dish
• Whisk
• Fork

Instructions

Step 1: Prepare the Spaghetti Squash

Preheat your oven to 400°F (200°C).

Carefully slice the spaghetti squash in half lengthwise. Scoop out all the seeds and stringy pulp using a spoon.

Brush the cut sides with olive oil and season evenly with salt and black pepper.

Place the squash halves cut-side down on a parchment-lined baking sheet.

Roast for 35–45 minutes, depending on the size of the squash, until a knife easily pierces the skin.

Remove from the oven and let the squash cool for about 10 minutes.

Using a fork, gently scrape the flesh into long spaghetti-like strands.

Transfer the strands to a bowl and lightly squeeze out any excess moisture using paper towels or a clean kitchen towel. This prevents the casserole from becoming watery.

Set aside.

Step 2: Cook the Broccoli

Bring a large pot of salted water to a boil.

Add the broccoli florets and cook for 2–3 minutes, just until bright green and slightly tender.

Drain immediately and rinse under cold water or place in an ice bath to stop the cooking.

Drain well.

Set aside.

Step 3: Make the Creamy Cheese Sauce

Place a large skillet over medium heat.

Melt the butter.

Add the diced onion and cook for about 5 minutes, stirring occasionally until soft and translucent.

Stir in the minced garlic and cook for another minute until fragrant.

Sprinkle the flour over the onions.

Whisk continuously for about 2 minutes to cook the flour without browning it.

Slowly pour in the milk while whisking constantly to prevent lumps.

Add the heavy cream and continue whisking until smooth.

Cook for 5–7 minutes, stirring frequently, until the sauce thickens.

Mix in:

• Dijon mustard
• Smoked paprika
• Garlic powder
• Onion powder
• Black pepper
• Salt
• Cayenne pepper (if using)

Reduce the heat to low.

Gradually stir in the cheddar cheese, one handful at a time.

Add the mozzarella cheese.

Finally stir in the Parmesan cheese.

Continue stirring until completely melted and silky smooth.

Taste and adjust seasoning if necessary.

Step 4: Combine Everything

Add the spaghetti squash strands into the cheese sauce.

Fold gently until evenly coated.

Add the cooked broccoli.

Mix carefully to avoid breaking the broccoli too much.

If using chicken or bacon, stir them in now.

The mixture should be creamy and evenly coated with cheese.

Step 5: Prepare the Topping

In a small bowl combine:

• Panko breadcrumbs
• Parmesan cheese
• Melted butter
• Chopped parsley

Mix until the breadcrumbs are evenly coated.

Step 6: Assemble

Lightly grease a baking dish.

Spread the cheesy squash mixture evenly into the dish.

Sprinkle the breadcrumb mixture evenly over the top.

For an extra cheesy finish, add an additional ½ cup shredded cheddar cheese before adding the breadcrumbs.

Step 7: Bake

Bake at 375°F (190°C) for 20–25 minutes until bubbling around the edges.

For a crispier topping, broil for 2–3 minutes while watching carefully to prevent burning.

Remove from the oven.

Allow the casserole to rest for 5–10 minutes before serving.

Serving Suggestions

Serve warm with:

• Grilled chicken breast
• Garlic bread
• Roasted salmon
• Baked turkey
• Green salad
• Roasted asparagus
• Sautéed mushrooms

Storage

• Refrigerate leftovers in an airtight container for up to 4 days.
• Freeze for up to 2 months.
• Thaw overnight in the refrigerator before reheating.

Reheating

• Oven: Bake at 350°F (175°C) for 15–20 minutes until heated through.
• Microwave: Heat individual portions in 1-minute intervals, stirring between each, until hot.
• Add a splash of milk if the sauce has thickened too much.

Tips for Success

• Roast the squash until just tender to avoid mushy strands.
• Drain excess moisture from the squash for the creamiest texture.
• Shred your own cheddar cheese for a smoother sauce, as pre-shredded cheese often contains anti-caking agents that can affect melting.
• Slightly undercook the broccoli so it stays vibrant and doesn’t become too soft after baking.
• Let the casserole rest before serving so the cheese sauce can set slightly.
• For extra flavor, mix in crispy bacon, shredded rotisserie chicken, or sautéed mushrooms.
• Garnish with fresh parsley, chives, or extra Parmesan just before serving for a bright, flavorful finish.