How to Make It
In a medium saucepan of salted boiling water, cook the cauliflower until very tender, about 7 minutes. Drain well and pat dry. In a medium bowl, puree the cauliflower with a potato masher or fork. Transfer the cauliflower to a colander and let drain until cooled completely.
Meanwhile, preheat the oven to 350°. Grease a 6-cup soufflé dish with 1 tablespoon of the butter and set it on a rimmed baking sheet. In a medium saucepan, melt the remaining 7 tablespoons of butter. Add the flour and whisk over moderate heat until bubbling, about 3 minutes. Gradually whisk in the milk and bring to a boil. Simmer over moderately low heat, whisking, until thickened and no floury taste remains, about 7 minutes. Season the béchamel with salt and pepper. Scrape into a large bowl and let cool, stirring occasionally.
Stir the cauliflower puree into the béchamel, then fold in the cheese and chives. In a medium bowl, beat the eggs until frothy, then gently fold them into the cauliflower béchamel. Scrape the soufflé base into the prepared dish and bake for about 1 hour and 10 minutes, until puffed and browned; serve right away.