Cauliflower Casserole (Au Gratin)

4.54 from 13 votes

Cauliflower Casserole (Au Gratin)

This cauliflower casserole is a delicious side dish or vegetarian main course, perfect for simple dinners and fancy enough for holidays.

Course Side Dish

Cuisine American

Keyword casserole, cauliflower, side dish

Dietary Restrictions Vegetarian

Prep Time 20

Cook Time 20

Total Time 40

Servings

Calories 299.15kcal

Author Lisa Lotts

Ingredients

1 head cauliflower
2 ½ tablespoons unsalted butter
2½ tablespoons all purpose flour
¼ teaspoon nutmeg
¾ teaspoon dry mustard
1 teaspoon kosher salt
½ teaspoon black pepper
2 cups milk
1½ cups Gruyère cheese grated

FOR BREADCRUMB TOPPING:

2 slices bread white, wheat, rye, sourdough, etc.
4-5 sprigs parsley
1½ teaspoons butter

US Customary - Metric

Instructions

Preheat the oven to 375°. Spray a small casserole dish with vegetable spray and set aside.
Trim 1 head cauliflower into bite-sized florets and transfer to a microwave-safe container. Add about ¼" cup of water and cover with plastic wrap. Microwave on high for about 5 minutes or until the cauliflower is tender. See other methods in the notes below.
In a medium saucepan, heat 2 ½ tablespoons unsalted butter over medium-high heat. When butter is melted and bubbly, whisk in 2½ tablespoons all purpose flour, ¼ teaspoon nutmeg, ¾ teaspoon dry mustard, 1 teaspoon kosher salt and ½ teaspoon black pepper. Stir until the butter and dry ingredients form a paste or roux.
Add 2 cups milka little at a time, whisking constantly. Add more milk once the mixture thickens and bubbles. Continue in this manner until you've used all the milk and have a creamy white sauce. Cook, stirring and scraping the sides and edges until the milk mixture thickens and comes to a low boil. Cook for one minute and remove from the heat.
Add1½ cups Gruyère cheese cheese; stir until melted. Add the drained and cooled cauliflower to the cheese mixture, then fold the florets into the sauce until coated.
Tear 2 slices bread into pieces and transfer to a mini food processor. Add 4-5 sprigs parsley and 1½ teaspoons butter. Pulse until the bread and parsley are finely chopped.
Spray a 1-quart baking dish with vegetable spray and spread the cauliflower mixture into an even layer in the dish. Sprinkle with about ½ cup of the buttered bread crumbs.
Bake for 18-20 minutes, until bubbly. Turn the broiler to high and cook for 1-2 more minutes, or until the breadcrumbs are nicely browned. Remove from oven and rest for 5-10 minutes before serving.

Video

Notes

You can also cook cauliflower florets on the stovetop: blanch them in boiling water for 3-4 minutes, then drain well and set aside, uncovered to cool.

Or steam them using a steamer basket set over a pan of boiling water. Cover and steam for 8-10 minutes until the vegetable is tender. Set aside uncovered to cool.

Storage Options:

You can make the cauliflower au gratin several hours ahead and store it in the fridge; bake it off just before you want to serve it.
Usually, I would recommend an airtight container for storage, but in order to preserve the crunchy breadcrumb topping, I store leftovers in the same dish covered with foil in the refrigerator.
Reheat at 350°F for 10-15 minutes or until hot and bubbly.
I don't recommend freezing the casserole as the cauliflower can weep liquid and make the dish watery.

Nutrition