Step 1

Position a rack in the middle of the oven and preheat to 400 degrees. Have on hand a steamer basket that fits into a large Dutch oven or other large pot.

Step 2

Pull the leaves off the cauliflower and trim the stem. Using a paring knife, cut around the core to remove it; halve the core lengthwise and thinly slice it crosswise. Transfer to the Dutch oven.

Step 3

Cut the head into 1/2-inch-thick slabs. Cut the stems from the slabs to create florets that are about 1 1/2 inches tall. Thinly slice the stems and transfer them to the Dutch oven, along with 1 cup of the florets. Reserve the remaining florets and any small pieces created during trimming.

Step 4

Add the water and butter to the pot, and set a steamer basket on top. Set the heat to high and bring to a boil. Reduce the heat to medium, add the reserved florets and small pieces to the steamer basket, cover the pot and cook until the florets in the basket can be easily pierced with a paring knife, 10 to 12 minutes. Remove the basket, drain the florets, and transfer them to an 8-inch square baking dish.

Step 5

Reduce the heat to low, cover the pot, and continue cooking the stem mixture until very soft, about 10 additional minutes. Transfer the stem mixture and cooking liquid to a blender. Add 3 tablespoons of the nutritional yeast, the salt, cornstarch, pepper, smoked paprika, chipotle and cayenne. Process until smooth and velvety, about 1 minute. The puree should be thick but pourable; adjust the consistency with more water, as needed. Taste, and season with more salt and/or pepper, as needed.

Step 6

Transfer the puree to the baking dish and toss gently with the florets to evenly coat them. Smooth the top with a spatula.

Step 7

In a small bowl, mix the panko with the remaining 3 tablespoons nutritional yeast and sprinkle it evenly over the top of the cauliflower mixture in the baking dish.

Step 8

Bake for 13 to 15 minutes, or until the sauce bubbles around the edges. Let stand for at least 10 minutes, then sprinkle with the chives and serve hot or warm.