This make-ahead broccoli and cauliflower casserole has delicious creamy cheddar leek sauce and crunchy panko breadcrumb topping. It can be prepared a day ahead or you can make it and serve it right away.

a white casserole dish with broccoli and cauliflower casserole with browned breadcrumbs on top

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I originally published this recipe on November 13th, 2015. I have updated some of the content to share it with you today. This post contains affiliate links.

Why We Love This Broccoli and Cauliflower Casserole

This casserole is a great addition to a holiday meal or can be served as a side dish for a Sunday supper. The savory yet light cream sauce pairs well with Pork Loin Roast, salmon baked in foil, baked crispy chicken and steak.

Because it can be made ahead, it is great for entertaining. Not only is it vegetarian, but it can be made gluten-free and lactose-free if desired so pretty much everyone can enjoy it.

Cauliflower Broccoli Casserole Ingredients

  • Cauliflower: You will need an entire head of cauliflower. Look for a medium sized head free from brown spots. Remove any leaves, and cut the core out before cutting into florets.
  • Broccoli: You will need two large broccoli crowns (about 1 pound.)
  • Olive Oil: To make this lower in saturated fat, we used olive oil instead of butter. The oil is used to saute the leeks, and it helps to make the breading on top brown and crisp nicely.
  • Leek: The leek adds delicious flavor to the cheddar sauce. You only need the white and pale green parts, so you can chop off the green parts. Use them to make chicken stock. Follow instructions for how to clean a leek here.
  • Salt: Note that we recommend table salt for this recipe. You may use kosher salt instead, but you will want to double it.
  • Flour: To thicken the sauce, we used all-purpose flour. For gluten-free alternatives, we suggest using a cornstarch slurry instead of trying to use gluten-free flours. See more gluten-free tips below in our FAQs section.
  • Milk: You can use regular milk or lactose-free milk. To keep this lower in calories, we used fat-free (skim) milk, but any type of milk will work.
  • Cheddar: For the cheddar sauce, look for the sharpest available cheddar. That will give the sauce the strongest cheese flavor with only 1 1/2 cups.
  • White Pepper: Creamy sauces are great with the flavor of white pepper. Black pepper can be substituted if unavailable.
  • Panko: For crunchy golden topping, use panko breadcrumbs instead of regular fine breadcrumbs. IF you can find it, use whole-wheat for a tiny bit of additional fiber.
  • Paprika and Garlic Powder: To season the breadcrumb mixture and give it color, use a combination of garlic powder and paprika.

How To Make A Casserole with Broccoli and Cauliflower

blanching the broccoli and cauliflower
  • STEP 1: Begin by bringing a large pot of salted water to a boil for blanching the vegetables. Set up a bowl of ice water.
  • Step 2: Blanch cauliflower 3 minutes in boiling water. Remove from the water with a slotted spoon or small strainer and transfer immediately to the ice bath to stop it from cooking. Repeat with the broccoli, cooking for 3 minutes, and shocking in the ice bath. Drain the vegetables very well. Reserve bowl for mixing in step 7.
making the cheddar leek sauce
  • Step 3: Prepare cheese sauce. Heat 2 tablespoons oil in a large saucepan over medium-high heat. Add leek and ¾ teaspoon salt and cook, stirring often until the leek is soft, 4 to 5 minutes.
  • Step 4: Sprinkle the flour over the leek and stir to coat and the flour is evenly moistened.
mixing the cheese into the sauce
  • Step 5: Add milk and bring to a simmer, over high heat, stirring constantly. Cook until bubbling and thickened, 1 to 2 minutes longer.
  • Step 6: Remove the sauce from the heat and stir in cheese and pepper until the cheese is completely melted into the sauce.
mixing the veggies and sauce and getting it ready to bake
  • Step 7: Preheat oven to 350 degrees F. Coat a 2 ½ quart baking dish with cooking spray. Mix the vegetables and cheese sauce together in the reserved bowl.
  • Step 8: Transfer the veggie mixture to the prepared baking dish.
the panko mixture and topping the casserole before baking
  • Step 9: Stir panko, the remaining 1 teaspoon oil, paprika and garlic powder in a small dish until evenly moist. Top the broccoli and cauliflower mixture with the panko mixture.
  • Step 10: Bake until the casserole is hot all the way through, the sauce is bubbling and the vegetables are tender, 28 to 35 minutes. Let cool 15 minutes before serving.
broccoli and cauliflower casserole in a white ceramic casserole dish with handles

FAQs, Tips and Tricks For This Recipe

Can this Cauliflower and Broccoli Casserole be made gluten-free

To make this gluten free, you’ll need to change up the sauce technique slightly. Here’s how:
Cook the leeks as directed. 
Add 1 1/2 cups milk and heat until just steaming.
Whisk the remaining 1/2 cup milk with 2 tablespoons plus 1 teaspoon cornstarch in a small bowl.
Drizzle the cornstarch slurry into the steaming leek and milk mixture while whisking. Bring to a simmer while whisking.
Remove from the heat and stir in the cheese and pepper.
You will also have to purchase gluten-free panko. I like Ian’s brand. 

Can this casserole be made lactose free?

To make this casserole lactose free, use a lactose free milk such as lactaid or Organic Valley Lactose Free milk and Cabot Cheddar (which is lactose free.)

Can other vegetables be substituted?

You can use all cauliflower or all broccoli if you like. You could also substitute in halved Brussels sprouts for one or the other, but note that you will need to blanch it for 4 minutes 30 seconds.

Can this Broccoli and Cauliflower Casserole be made ahead of time?

This recipe can easily be prepped in advance and cooked just before you plan on serving it.  To make this casserole ahead of time:
1. You’ll need to make the cheese sauce and blanch the veggies as directed in the recipe.
2. Then combine everything and transfer to your casserole dish.
Cover the casserole in foil and refrigerate up to 24 hours in advance. (note; do not add the breadcrumbs yet as they will pull too much moisture out of the casserole and will not crisp up again.)
3. Cook the casserole covered for 25 minutes.
4. Remove the cover, top with the breadcrumb mixture and bake until the casserole is hot all the way through, the sauce is bubbling and the vegetables are tender, 28 to 35 minutes.

a white casserole dish with broccoli and cauliflower casserole with browned breadcrumbs on top with a spoon in it

At Healthy Seasonal Recipes, we specialize in cooking with fresh veggies and creating weeknight meals. Sign up HERE to get more produce-forward dinner ideas for FREE! If you make this recipe, please come back and leave a star rating and review. I would love to hear what you thought! Happy Cooking! ~Katie

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Healthy Make-ahead Broccoli and Cauliflower Casserole with Creamy Cheddar Leek Sauce and Crunchy Panko Breadcrumb topping on HealthySeasonalRecipes.com

Broccoli and Cauliflower Casserole Recipe

5 Stars 4 Stars 3 Stars 2 Stars 1 Star

4.9 from 10 reviews

  • Author: Katie Webster
  • Total Time: 1 hour 15 minutes
  • Yield: 10 cups 1x
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Description

This make-ahead broccoli and cauliflower casserole is a healthy and delicious option for a covered dish for the holidays. The cauliflower and broccoli are coated in a creamy leek cheddar sauce and topped with crunchy panko breadcrumb topping.

Ingredients

Units Scale
  • 1 medium head of cauliflower
  • 2 large broccoli crowns (1 pound)
  • 2 tablespoons plus 1 teaspoon extra-virgin olive oil, divided
  • 1 large leek, white and pale green part only, sliced and washed
  • 3/4 teaspoon salt
  • 1/3 cup all-purpose flour
  • 2 cups fat-free milk (lactose-free if desired)
  • 6 ounces sharp lactose free cheddar, shredded (I used Cabot Alpine)
  • 1/4 teaspoon ground white pepper
  • 1/4 cup panko, preferably whole-wheat
  • 1 teaspoon paprika
  • 1/4 teaspoon garlic powder

Instructions

  1. Core cauliflower and cut into medium florets. Cut off broccoli stems and cut into florets. Meanwhile, bring a large pot of salted water to a boil. Set a large bowl of ice water to the side.
  2. Blanch cauliflower 3 minutes in boiling water. Remove from the water with a slotted spoon or small strainer and transfer immediately to the ice bath to stop it from cooking. Repeat with the broccoli, cooking for 3 minutes, and shocking in the ice bath. Drain the vegetables very well. Reserve bowl for mixing in step 7.
  3. Prepare cheese sauce. Heat 2 tablespoons oil in a large saucepan over medium-high heat. Add leek and ¾ teaspoon salt and cook, stirring often until the leek is soft, 4 to 5 minutes.
  4. Sprinkle the flour over the leek and stir to coat and the flour is evenly moistened.
  5. Add milk and bring to a simmer, over high heat, stirring constantly. Cook until bubbling and thickened, 1 to 2 minutes longer.
  6. Remove the sauce from the heat and stir in cheese and pepper until the cheese is completely melted into the sauce.
  7. Preheat oven to 350 degrees F. Coat a 2 ½ quart baking dish with cooking spray. Mix the vegetables and cheese sauce together in the reserved bowl.
  8. Transfer the veggie mixture to the prepared baking dish.
  9. Stir panko, the remaining 1 teaspoon oil, paprika and garlic powder in a small dish until evenly moist. Top the broccoli and cauliflower mixture with the panko mixture.
  10. Bake until the casserole is hot all the way through, the sauce is bubbling and the vegetables are tender, 28 to 35 minutes. Let cool 15 minutes before serving.

Notes

TO MAKE AHEAD: Prepare through step 8 (do not pre-heat oven in step 7.) Cover casserole in foil and refrigerate up to 24 hours in advance. Preheat oven, and bake casserole covered for 25 minutes. Remove foil and continue with topping with the breadcrumb mixture and baking as directed in step 5.

  • Prep Time: 30 minutes
  • Cook Time: 30 minutes
  • Category: Side Dish
  • Method: Baked
  • Cuisine: American

Nutrition

  • Serving Size: 1 cup
  • Calories: 171
  • Sugar: 3 g
  • Sodium: 377 mg
  • Fat: 10 g
  • Saturated Fat: 5 g
  • Carbohydrates: 12 g
  • Fiber: 2 g
  • Protein: 8 g

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