We’re skipping the white sauce here and instead, making the most of the cauliflower’s natural qualities of becoming a super creamy puree to bind this delicious side dish together.
With butter-toasted breadcrumb for a topping and a citrus herb gremolata (parsley, garlic, and lemon and orange zest), this side is sure to impress.
This cauliflower gratin gets its creaminess from more cauliflower rather than a heavy white sauce, and is brightened up with a fresh gremolata.
- Set oven rack in middle position and preheat to 400°F.
- Remove the outer leaves of the cauliflower and trim the stems. Cut around the core with a paring knife to remove, then cut the cores in half lengthwise and thinly slice. Set aside. Cut the head into 1/2-inch thick slabs, creating florets that are about 1 1/2 inches tall. Thinly slice stems and place with the sliced core. Transfer florets to a bowl and set aside. You should have about 3 cups of sliced stems and cores and 12 cups of florets.
- Combine sliced stems and cores, 2 cups of the florets, 3 cups of water, and 6 tablespoons of the butter in a Dutch oven. Bring to a boil over high heat.
- Place remaining florets in a steamer basket and place in the pot once the mixture is boiling. Cover and reduce heat to medium. Steam florets until they turn translucent and stem ends can easily be pierced with a paring knife, about 10-12 minutes.
- Remove the steamer basket and drain florets, then transfer to a bowl.
- Place the cover back on the pot reduce heat to low, and continue to cook stem mixture until very soft, about 10 minutes more.
- While the cauliflower cooks, melt the remaining 2 tablespoons of butter in a 10-inch skillet over medium heat. Add the panko and cook, stirring often, until golden brown, about 3-5 minutes. Transfer to a bowl and allow to cool. Once cool, stir in 1/2 cup of the parmesan.
- Transfer the stem mixture and cooking liquid to a blender. Add 2 teaspoons salt, 1/2 teaspoon pepper, mustard, nutmeg, cayenne, and the remaining 1/2 cup parmesan. Process until mixture is smooth and velvety, about 1 minute. The puree should be pourable; you can adjust the consistency with water if needed.
- With the blender running, add cornstarch slurry. Taste and season with salt and pepper if needed. Pour over cauliflower florets and toss gently until evenly coated.
- Transfer mixture to a 9×13-inch baking dish and use a spatula to smooth the top.
- Scatter the breadcrumb mixture evenly over the top. Transfer dish to the oven and bake until sauce is bubbling around the edges, about 13-15 minutes. Let stand for 20-25 minutes.
- To make the gremolata, combine all ingredients on a cutting board and chop even more finely. Sprinkle over gratin before serving.