Active Time

　　45 min

　　Total Time

　　55 min

　　We think of this gratin as a vegetable-driven version of everyone's favorite, mac and cheese. The nutty, sweet undertones of cauliflower are particularly suited to meld with the tangy, salty Cheddar and the spicy horseradish.

　　

Ingredients

Makes 8 servings

　　3 lb cauliflower (1 large head), cut into 1 1/2- to 2-inch florets

　　1/2 stick (1/4 cup) unsalted butter

　　2 tablespoons all-purpose flour

　　1 1/2 cups whole milk

　　6 oz sharp Cheddar, coarsely grated (2 cups)

　　1/2 cup finely chopped scallion greens

　　1/2 teaspoon salt

　　1/2 teaspoon black pepper

　　20 (2-inch) square saltine crackers

　　2 tablespoons drained bottled horseradish

　　

Step 1

Preheat oven to 450°F. Butter a 2-quart shallow baking dish.

　　

Step 2

Cook cauliflower in a 5- to 6-quart pot of boiling salted water until just tender, 6 to 8 minutes. Drain cauliflower well in a colander and transfer to baking dish.

　　

Step 3

While cauliflower cooks, melt 2 tablespoons butter in a 3- to 4-quart heavy saucepan over moderately low heat and whisk in flour. Cook roux, whisking, 3 minutes. Add milk in a slow stream, whisking, and bring to a boil, whisking frequently. Reduce heat and simmer sauce, whisking occasionally, 8 minutes. Remove from heat and add cheese, scallion greens, salt, and pepper, whisking until cheese is melted. Pour cheese sauce over cauliflower and stir gently to combine.

　　

Step 4

Coarsely crumble crackers into a bowl. Melt remaining 2 tablespoons butter in a small saucepan, then remove from heat and stir in horseradish. Pour over crumbs and toss to coat.

　　

Step 5

Sprinkle crumb topping evenly over cauliflower.

　　

Step 6

Bake gratin until topping is golden brown, about 10 minutes.