Cauliflower Gratin

The bitter cold of a Cincinnati winter brought me to cauliflower gratin. It was my first year away from home; unlike the warm winters in India that I was accustomed to, I was in the Midwest coping with ear-biting wind chills and snowy days. I often sought comfort and warmth in libraries and bookstores and it was during one of my trips to the library that I came across Jane Grigson’s Vegetable Book and its recipe for cauliflower gratin. The cauliflower—draped in a rich, savory mornay sauce and topped with a sprinkling of buttery bread crumbs—quickly became my go-to comfort meal. 

Though I’ve long since left Cincinnati, the dish remains a favorite of mine, so much so that I’ve tweaked it numerous times over the years to my liking. My version builds on the sweet and nutty  flavors of the cheeses. Cauliflower florets are coated in a velvety mornay sauce—a béchamel enriched with semi-firm cheeses like Swiss, Gruyère, or Parmigiano-Reggiano—then topped with breadcrumbs. A touch of miso paste brings a deep, savory flavor to the sauce as well.

The Best Way to Prepare Cauliflower for Gratin

To ensure that our gratin cooks evenly in the oven, we must first cook the cauliflower until tender. The question is: to blanch or not to blanch? Initially, I was curious to see if steaming the cauliflower in a baking dish tightly covered with foil would achieve the same results as blanching the cauliflower in a pot of salted water. After comparing the two methods side-by-side, I found that the oven-steamed cauliflower wasn’t exponentially more flavorful than the blanched cauliflower, nor was it significantly faster. In fact, the oven-steamed cauliflower took 25-to-30 minutes, while blanching—including the time it took to bring the water to a boil—took just about 10 minutes.

How to Make Mornay Sauce

In order to make a truly stellar mornay sauce, it’s essential to understand how a roux—a blend of fat and flour—works to thicken the soups and sauces it’s used in. To make a roux, you whisk flour into melted fat, cooking the starch for several minutes to cook out its raw flavor. This not only results in a more delicious sauce, but it also coats each starch granule in fat and reduces the risk of the flour clumping when you eventually whisk in the liquid, like stock or milk. 

The kind of starch and fat you use—as well as how long you cook your roux and how dark you want to take it—will determine the flavor and thickness of your sauce. (You can read more here in Daniel’s deep-dive.) Because we don’t want a particularly dark sauce—the darker the roux, the thinner the sauce—we’re going to cook the flour just until it loses its raw flavor before we add the milk. And while we do want a sauce with body, we also need to keep in mind that the addition of Gruyère and Parmigiano-Reggiano will substantially enrich the sauce. Here, a 1:1 ratio of flour to butter makes a thick but pourable sauce that doesn’t become too heavy once the cheeses are added.

Making an Umami-Packed Sauce

To highlight the savory notes of the sauce, I added white miso paste, which intensifies the flavor of the cheeses and also lends a slightly nutty flavor. As former Serious Eats editor Sho Spaeth wrote in his profile of Rich Shih, a mechanical engineer and koji authority, miso is made by fermenting soybeans with a koji mold called Aspergillus oryzae, transforming proteins into flavorful amino acids that our taste buds interpret as umami. Together with other glutamate-rich seasonings like onion powder and garlic powder, the sauce is savory and complex, highlighting the cauliflower’s natural sweetness.

Seasoning the Breadcrumbs

It’s possible to serve a gratin without a crunchy topping of toasted breadcrumbs, but what fun would that be? Here, I’ve chosen to season my breadcrumbs with za’atar, an essential ingredient in many Arab pantries. Za’atar refers to a specific plant that belongs to the oregano family and is indigenous to the Levant, though the term also, somewhat confusingly, is used to describe a spice blend made with the leaves of the plant. As Palestinian writer and Serious Eats contributor Reem Kassis mentioned in her za’atar recipe, it’s difficult to source fresh za’atar in the United States. While oregano is a suitable substitute if you’re making your own blend, it’s also possible to purchase mixes from companies like Burlap & Barrel and Milk Street. Earthy and herbaceous, za’atar adds a bright note that complements and offsets the richness of the cheese and cream in the gratin.