Look no further, this cauliflower broccoli au gratin recipe not only satisfies but will also impress. It's creamy, cheesy and spiced just right! It's a side dish that your family will love!

In This Post

Why You'll Love This Cauliflower Broccoli Au Gratin Recipe
Vegetable Au Gratin Ingredients
How To Make Cauliflower Broccoli Au Gratin
Tips & Tricks
What Cheese Do I Use?
More Side Dishes
Creamy Cauliflower and Broccoli Au Gratin

I originally posted this recipe in 2020, right after I had my daughter. Why is that important you ask– a good friend of mine introduced me to Trader Joe's Cauliflower and Broccoli Au Gratin while pregnant. I took one bit and I was in heaven. So of course I had to re-create it.

This might just be the best cauliflower broccoli au gratin recipe that I have ever had. It's the kind of recipe that satisfies without weighing you down (talking to you au gratin potatoes.) This is a recipe that is on repeat and I'm certain it will for you too.

Why You'll Love This Cauliflower Broccoli Au Gratin Recipe

Insanely creamy
Packed with flavor from the spices and cream sauce
Ridiculously cheesy, as an au gratin should be!
The cheese cause to cauliflower and broccoli ratio is perfect
Crunchy breadcrumb topping takes it over the top

Vegetable Au Gratin Ingredients

Vegetables: Traditionally au gratin is made with potatoes but we're swapping them out for a combination of broccoli and cauliflower florets. You can either buy them pre-cut or cut them yourself– you just want all pieces to be roughly the same size.
Butter: Butter is in the base of the cheese sauce and used in the breadcrumb topping, adding so much flavor.
Flour: Using flour helps thicken the cheese sauce just like in this slow cooker chicken and rice soup– not a cheese sauce it has the same job, thicken.
Milk: The milk begins the sauce and gradually thickens as it cooks.
Shredded Cheese: We're using parmesan and cheddar cheese in this recipe. Though, it's a pretty forgiving recipe so you can always use what you have on hand.
Spices: Back to the basics here but each offers just the right amount of spice– salt, pepper, garlic powder and onion powder.
Breadcrumbs: The star of that breadcrumb topping that gets crispy as it bakes. Do yourself a favor and don't forget this step.

How To Make Cauliflower Broccoli Au Gratin

Have you ever made au gratin from scratch before? It looks intimidating but don't fret, it's easy. I also include some tips and tricks further down to make it even easier!

Steam the veggies: Steam or boil the cauliflower and broccoli until just tender— you don't want them fully cooked since they will finish in the oven.
Begin the cheese sauce: Melt the butter on the stove, then add flour. The flour soaks up the butter making a "roux." Cook the roux for 1 minute, this helps cook out of the flour taste. If you're not familiar with a roux, pronounced "roo", it's a way to thicken things like gravy, sauce, macaroni and cheese or soup! Making a roux is very simple with equal parts butter and flour, letting it cook down and then adding the liquid (in this case, the milk.)
Add the milk and spices: Whisk in the milk, salt, pepper, garlic powder, and onion powder. Bring it to simmer and whisk in the cheese until smooth.
Combine: Add a few spoonfuls of the cheese sauce to the bottom of the baking dish. Then, add the veggies. Pour the remaining cheese sauce on top and gently stir together.
Make the breadcrumb topping: Melt the butter and stir in the Panko. Sprinkle over the top.
Bake: Bake for 17-20 minutes until bubbly and slightly brown on the top.

Tips & Tricks

While this is an easy recipe, here's a few tips to make it even easier!

Use steam-in-bag vegetables– that's right, use that shortcut! For those extra busy nights or you really just don't feel like pulling out a pot to steam vegetables... there's no shame. I've done it a handful of times! However, if using this option, steam for 1 minute less than it says since the'll finish cooking in the oven.
Make the breadcrumb topping while the vegetables steam. No matter how you steam the vegetables, do this step in parallel. It's quick but another step done ahead of time.
Use whole milk for the cream sauce. In a pinch I've used 1% or 2% milk but it's THAT MUCH BETTER when you use whole milk.

What Cheese Do I Use?

For a truly remarkable au gratin, use a combination of cheeses. I recommend using white cheddar and parmesan for the best flavor. Grate it at home if you can, so it's soft and fresh– pre-shredded has additives to make it a bit sturdier. I love this cheese grater if you're in the market for one!

We're looking for this level of a creaminess: