Broccoli Cauliflower Bake (Vegetable Au Gratin) Recipe

I’m sharing my Broccoli Cauliflower Bake, where broccoli and cauliflower florets meet a creamy white sauce and a cheesy breadcrumb topping in a classic vegetable au gratin.

I never thought a veggie side could steal the show until I discovered my Broccoli Cauliflower Bake. Broccoli florets and sharp cheddar cheese combine into something creamy and kind of indulgent, like it shouldn’t be this addictive but it totally is.

People always ask what’s the secret, and I just grin because there’s a tiny twist I keep changing that somehow makes everyone go back for more. It looks simple but it has attitude, and it disappears fast at a dinner.

Try it and you’ll see why I keep making it, even when I tell myself to slow down.

Ingredients

• Broccoli: high in fiber vitamin C and K adds fresh grassy bite
• Cauliflower: low carb nice mild nutty flavor soaks up cheesy sauce
• Sharp cheddar: gives tangy rich melt protein and calcium not overly sweet
• Parmesan: salty umami boost a little goes far for savory depth
• Whole milk: makes the sauce creamy adds calories and calcium milky notes
• Heavy cream: optional but makes it silkier and richer ok to skip
• Garlic and onion: give aromatic depth savory backbone they ain’t sweet
• Panko crumbs: crunchy topping adds texture and browned buttery crispness

Ingredient Quantities

• 4 cups broccoli florets, roughly chopped
• 4 cups cauliflower florets, roughly chopped
• 4 tablespoons unsalted butter
• 1/4 cup all purpose flour
• 2 cups whole milk
• 1/2 cup heavy cream optional
• 1 small onion, finely chopped
• 2 cloves garlic, minced
• 1 teaspoon Dijon mustard
• 1 teaspoon kosher salt
• 1/2 teaspoon freshly ground black pepper
• 1/8 teaspoon ground nutmeg or a pinch
• 2 cups sharp cheddar cheese, shredded
• 1/2 cup grated Parmesan cheese
• 3/4 cup panko breadcrumbs (or regular breadcrumbs)
• 2 tablespoons melted butter for the crumbs
• 2 tablespoons chopped fresh parsley optional

How to Make this

1. Preheat oven to 375 F (190 C). Grease a 9×13 inch baking dish or similar with a little butter and set aside.

2. Bring a large pot of salted water to a boil. Add the broccoli and cauliflower florets and cook 3 to 4 minutes until just tender but still crisp, then immediately drain and plunge into a bowl of ice water to stop cooking. Drain very well and pat dry with paper towels.

3. In a medium saucepan melt 4 tablespoons unsalted butter over medium heat. Add the finely chopped onion and cook until soft and translucent about 4 minutes, stir in the minced garlic and cook 30 seconds more.

4. Sprinkle the 1/4 cup all purpose flour over the onion mixture and stir constantly for 1 to 2 minutes to cook the raw flour taste. Slowly whisk in the 2 cups whole milk and the 1/2 cup heavy cream if using, whisking constantly so no lumps form. Bring to a simmer until the sauce thickens, about 3 to 5 minutes.

5. Stir in 1 teaspoon Dijon mustard, 1 teaspoon kosher salt, 1/2 teaspoon black pepper and a pinch or 1/8 teaspoon ground nutmeg. Remove from heat and stir in 1 1/2 cups shredded sharp cheddar and the 1/2 cup grated Parmesan until smooth. If sauce is too thick add a splash more milk, too thin simmer a minute more.

6. Toss the drained broccoli and cauliflower with the cheese sauce until everything is evenly coated, then transfer to the prepared baking dish. Sprinkle the remaining 1/2 cup shredded cheddar evenly over the top.

7. In a small bowl combine 3/4 cup panko breadcrumbs with the 2 tablespoons melted butter and the 2 tablespoons chopped fresh parsley if using. Scatter the buttery crumbs over the cheese layer.

8. Bake uncovered at 375 F (190 C) for 20 to 25 minutes until bubbly and the top is golden brown. If you want extra browning you can broil 1 to 2 minutes at the end but watch it closely so it doesn’t burn.

9. Let the bake rest 5 to 10 minutes before serving so the sauce sets a bit. Sprinkle a little extra parsley for color and serve hot.

Equipment Needed

1. Oven set to 375 F (190 C)
2. 9×13 inch baking dish, greased
3. Large pot for blanching the broccoli and cauliflower, lid optional
4. Colander or strainer to drain the veggies
5. Large bowl for an ice bath and for cooling, get lots of ice
6. Medium saucepan for the cheese sauce
7. Whisk to smooth the roux and sauce
8. Chef knife and cutting board for chopping the florets and onion
9. Measuring cups and spoons (and a box grater if you shred your own cheese)

FAQ

Broccoli Cauliflower Bake (Vegetable Au Gratin) Recipe Substitutions and Variations

• Unsalted butter — quick swaps
  • Salted butter, use the same amount and cut back on the recipe salt a little
  • Olive oil, use about 3 tablespoons for 4 tablespoons butter, gives a bit of fruity flavor
  • Ghee, same amount, for nuttier richer taste and higher smoke point
• Whole milk or heavy cream — lighter or dairy free options
  • Half and half, use it in place of whole milk plus cream for similar creaminess
  • Evaporated milk, pantry friendly and richer than regular milk, use same volume as milk
  • Unsweetened soy or oat milk, use same amount, add 1 tablespoon melted butter if you want more richness
• Sharp cheddar cheese — other melters that work
  • Gruyere, melts smooth and adds a slightly nutty flavor
  • Monterey Jack, milder and very melty, good if you want less sharpness
  • Aged Gouda, for a smoky sweet twist, use slightly less because it can be strong
• Panko breadcrumbs — for the crunchy topping
  • Regular breadcrumbs, they give a denser crust but still tasty
  • Crushed buttery crackers like Ritz, gives extra flavor and crunch
  • Gluten free breadcrumbs or crushed cornflakes, for GF option with good crisp

Pro Tips

1) Dry the veggies really well after the ice bath. Any leftover water will thin the sauce and make the bake soggy. Let broccoli and cauliflower sit in a colander for a few minutes, then pat with paper towels, even press with a clean kitchen towel if you can.

2) Shred your own cheese from a block and taste the sauce before you add the cheese. Pre-shredded stuff has anti-caking agents and wont melt as smooth. Also, the sauce should be seasoned before cheese goes in because cheddar and Parmesan add salt. If the sauce gets too thick, thin with a splash of milk, too thin, simmer a minute more until it coats the spoon.

3) For a crisp topping, toast the panko first. Mix crumbs with the melted butter, spread on a sheet and give them a quick 5 to 8 minute toast in the oven until golden, then sprinkle on top right at the end so they stay crunchy. Broil for 1 minute if you want extra color but watch it like a hawk so it doesn’t burn.

4) Make-ahead & reheating hacks: you can assemble up to 24 hours ahead and refrigerate. If chilled, let it sit at room temp 20 minutes before baking or add 10 to 15 minutes to the bake time. For leftovers reheat covered at 350 F for about 20 minutes, then uncover and bake a few minutes to crisp the top.