Cauliflower Au Gratin made with fresh roasted cauliflower, onion, and bell peppers in a creamy, cheesy sauce topped with breadcrumbs broiled for a crispy crust!
Preheat oven to 400°F. Line a baking sheet with parchment paper. Place cauliflower, bell pepper, and onion on the baking sheet and bake for 20 minutes.
While the vegetables are cooking, melt 4 tablespoons of butter in a saucepan over medium heat. Add flour and whisk until flour begins to brown, then whisk in spices.
Add milk and whisk until mixture begins to thicken. Add cheese and stir until melted. Remove from heat and set aside.
Grease a large casserole dish. When vegetables are done, remove from sheet pan and add to casserole dish. Pour cheese sauce over cauliflower and stir to mix everything together.
In a separate bowl stir together breadcrumbs and melted butter. Make sure breadcrumbs are completely wet. Sprinkle on top evenly.
Bake uncovered for 15-20 minutes, or until breadcrumb topping is golden brown. Turn on broiler for the last minute or two if the topping isn't browned, watching closely to make sure it doesn't burn.
Notes
Click on the time in the instructions to start a timer!Cheese. It's best to shred the cheese yourself from a block. This prevents any unnecessary ingredients that might prevent the cheese from melting into your sauce. Substitutions.
Swap the cauliflower for broccoli, green beans, or squash.
Use heavy cream or half and half instead of 2% milk for a richer texture.
You can swap the spices for Ranch seasoning or taco seasoning! Or try fresh herbs like parsley or thyme. Or add cooked chicken.
Add red pepper flakes, cayenne pepper, or diced jalapeños to make it spicy.
Make it Vegan
Swap the butter with vegan butter
Use plain almond milk or vegetable broth instead of milk. If you use broth, it will be more like a gravy, but still tasty!
Use a good melting vegan cheese.
StorageYou can store cauliflower au gratin in an airtight container in the refrigerator for 3-4 days. This recipe does not freeze well.Make AheadYou can make this recipe the day before. Follow all steps as written, but right after you add the breadcrumb topping, wrap tightly and refrigerate. Right before serving, bake for about 20 minutes at 400°F, or until topping is golden brown. If the top is getting too toasty, cover with tinfoil until it's done baking (careful - it's hot!).