I enjoy greens for their earthy sweetness, but on their own they can be rather austere. So when I wanted a greens-based side dish for the holidays, I opted for a gratin. You don’t come across green gratins every day, and when you do they’re often drowned in cream, like creamed spinach. I wanted my gratin to be just a little richer than I normally make greens: I’d parcook the leaves, add some dairy and a bread-crumb topping, and finish everything in the oven.
One of the big challenges here is that most types of greens wilt down significantly when cooked: You start with an abundance and end up with a dearth. Some recipes compensate for this by adding potatoes or a second vegetable, but I wanted pure greens.
To avoid a squat, dense gratin, I strategically selected two types of greens. First, curly kale: Its sturdy, ruffled leaves would maintain some structure after cooking and keep the gratin sufficiently voluminous. Second, Swiss chard: Its delicate leaves collapse when cooked, but its plentiful tender stems can also be softened to add bulk. In a 1:2 ratio, the gutsy kale and mineral-y chard made great flavor partners, too.
To serve eight to 10 people, I needed 3 pounds of greens, which meant that I’d need to parcook heaps and heaps of leaves before assembling the gratin. Blanching or sautéing the leaves—the two strategies that most recipes call for—would require cooking in several smaller batches. Instead, I turned to steaming: I brought 2 cups of water to boil in a Dutch oven, loaded in the heftier kale, and covered the pot. After 5 minutes, the kale had wilted enough for me to stir in the more delicate chard. This way, all the leaves cooked efficiently and evenly.
As the greens drained, I considered the dairy component, which for a gratin is often cream thickened with a roux. But every iteration I tried was stodgy. Why not skip the roux and simply pour in the cream? I added only as much cream (spiced with fresh nutmeg) as the parcooked leaves could hold without making the gratin liquid-y, which amounted to 1 cup. The cream just coated the greens, contributing silky richness without masking the vegetal flavors.
For the topping, I pulsed rustic white bread in a food processor to create craggy crumbs. (While the processor was out, I used it to finely chop an onion and the chard stems, which I then sautéed with fresh thyme and stirred into the steamed greens.) I seasoned the crumbs with Parmesan and garlic and drizzled in some olive oil to help them crisp. Next I transferred the creamy greens to a baking dish, sprinkled on the topping, and baked the casserole until it bubbled and browned. Here was a winning gratin for the holidays—or for any day.