Step 1 of 16
Three-Cheese Garlic Cauliflower Gratin
Preheat the oven to 400°F.
Step 2 of 16
Three-Cheese Garlic Cauliflower Gratin
Line a large baking sheet with parchment paper. Set aside.
Step 3 of 16
Three-Cheese Garlic Cauliflower Gratin
Spray a 9-inch square baking dish with nonstick cooking spray. Set aside.
Step 4 of 16
Three-Cheese Garlic Cauliflower Gratin
Chop the cauliflower into 1-inch florets. Arrange the florets on the lined baking sheet. Drizzle with olive oil and season with salt and black pepper. Stir with rubber spatula to distribute the oil.
Step 5 of 16
Three-Cheese Garlic Cauliflower Gratin
Roast the cauliflower on middle rack of oven until the oil is sizzling and the outsides of the florets are slightly softened, about 10 minutes.
Step 6 of 16
Three-Cheese Garlic Cauliflower Gratin
Remove the baking sheet from the oven. Reduce the oven temperature to 375°F.
Step 7 of 16
Three-Cheese Garlic Cauliflower Gratin
Finely mince the garlic.
Step 8 of 16
Three-Cheese Garlic Cauliflower Gratin
In a large pot over medium heat, melt the butter. Add the garlic and sauté until fragrant, about 30 seconds. Sprinkle the flour into the pot and whisk to thoroughly combine. Continue whisking until the roux turns slightly golden and begins to smell toasty, 1-2 minutes.
Step 9 of 16
Three-Cheese Garlic Cauliflower Gratin
Slowly stream the milk into the pot while continuing to whisk. Cook the mixture, whisking steadily, until it begins to thicken and bubble, 4-5 minutes.
Step 10 of 16
Three-Cheese Garlic Cauliflower Gratin
Once bubbling, turn off the heat. Add shredded cheddar, Gruyere cheese, salt, and black pepper to the pot. Whisk slowly until the cheeses are fully melted and the sauce is smooth.
Step 11 of 16
Three-Cheese Garlic Cauliflower Gratin
Once the sauce is smooth, add the roasted cauliflower. Stir until the florets are thoroughly coated.
Step 12 of 16
Three-Cheese Garlic Cauliflower Gratin
Pour the contents of the pot into the greased baking dish.
Step 13 of 16
Three-Cheese Garlic Cauliflower Gratin
Place the bread crumbs, Parmesan, cheddar cheese, salt, and black pepper in a medium mixing bowl. Mix with a fork to combine. Add melted butter to the bowl, and stir until all the breadcrumbs are moistened. Sprinkle the crumbs in an even layer over the cauliflower.
Step 14 of 16
Three-Cheese Garlic Cauliflower Gratin
Bake the gratin on middle rack of oven until the edges are bubbling and the top is golden brown, 18-22 minutes.
Step 15 of 16
Three-Cheese Garlic Cauliflower Gratin
Check to see that gratin is done. Remove from oven or add time as needed.
Step 16 of 16
Three-Cheese Garlic Cauliflower Gratin
Allow gratin to rest for 10 minutes. Plate and serve.