This baked Cauliflower Gratin is an easy, cheesy, make-ahead side dish that’s great for serving a crowd. A perfect recipe for the holidays!
For the Filling:
- 1 large head of cauliflower, trimmed and cut into large chunks (about 2 1/2 lbs or 6–7 heaping cups)
- 3 tablespoons butter, plus more for greasing the dish
- 1/4 cup all purpose flour
- 1 1/2 cups reserved cooking water
- 1/4 cup heavy cream
- 2 teaspoons Kosher salt, plus more to taste
- 1/2 tsp freshly ground pepper, or to taste
- 1/4 teaspoon fresh nutmeg
- 6 ounces Gruyere cheese, grated (about 3 cups), divided
For the Topping:
- 3 tablespoons butter
- 1 clove garlic, finely minced
- 1 1/4 cups panko breadcrumbs
- 1 teaspoon fresh thyme leaves
- salt and pepper to taste
Add the cauliflower to a medium pot, then add just enough water to barely cover. The goal is to use less water in order to achieve a more concentrated cauliflower flavor, so it’s okay if some pieces are sticking out of the top. Bring the water up to a simmer, then cover and cook until the cauliflower pieces are al dente, about 2-3 minutes. Drain the cauliflower well and reserve the cooking water.
Preheat the oven to 400 degrees F and butter the inside of a medium casserole dish. Melt butter in a medium pot over medium heat, then whisk in the flour until it absorbs all the butter, about 1-2 minutes. Slowly whisk in 1 1/2 cups of the reserved cauliflower cooking water, then continue whisking until it comes up to a boil. Lower the heat, continue whisking, and cook for 2-3 minutes until thickened. Whisk in the heavy cream, salt and pepper, then turn off the heat. Stir in the nutmeg and 1/3 of the Gruyere cheese (about 1 cup) until the cheese is melted.
Add the well-drained cauliflower to the cheese sauce and mix to combine. It’s important that your cauliflower doesn’t have a lot of excess moisture or it will make the sauce watery. Taste for seasoning and adjust as needed – it will likely need a bit more salt.
Scrape the cauliflower mixture into the buttered casserole dish, being sure to get every last bit of cheese sauce in there. Sprinkle with the remaining Gruyere cheese, then set aside while you make the topping.
For the topping, melt the butter in a medium sauté pan over medium heat, then add the garlic and stir around until it starts to sizzle. Add the panko breadcrumbs, thyme leaves and a pinch of salt and pepper, then continue to stir around until light golden brown, about 5 minutes.
Spread the breadcrumbs on top of the cauliflower in an even layer, then pop it in the oven. Bake for about 20 minutes, or until the breadcrumbs have darkened a few shades and the sides are bubbling up. Allow the gratin to cool down for about 10 minutes before serving.
This recipe can be made entirely in advance. Reheat in a 350 degree F oven covered for about 15 minutes, then remove the cover and bake for another 10-15 minutes until bubbling around the sides.
Keywords: cauliflower, au gratin, Gruyere, cheese, Thanksgiving, Christmas, side dish, easy, healthy