Usually the thing to ask when using salt is: how can I make the most of the interplay between salt and food? There’s texture to consider, the mineral flavors of the salt itself, and the visual cues that sensuously salted food can provide to get the engines of your appetite revving. A spinach gratin is a slightly difficult character in this regard. Gratin is incredibly delicious, easy to eat, and naturally accommodates a variety of dishes, but its nature is to avoid acting like the life of the party. Also, much of the salt comes from the cheese, and the general texture of the dish is so full and rich that it leaves little room for any but the most aggressive salt crystals to have an impact on the mouthfeel of the dish. It takes an aggressive salt to shine against the backdrop of such a dish with sufficient luminosity to actually illuminate it without overwhelming it with saltiness. Two salts jump to mind: Maine Coast Sea Salt and Moroccan Atlantic Sea Salt. The salts have hard, bright, faintly hot but minerally flavors and a somewhat hard crunch, so you don’t need a lot for the salt to contribute a note of rowdiness to the spinach gratin. A few pinches on the top of a gratin will greet your lips with something unexpected, an in-your-face attitude that awakens you to the full pleasure of the gratin’s comforting flavors.
Makes 4 servings
1 tablespoon extra-virgin olive oil
4 ounces shiitake mushrooms, stems trimmed, caps sliced about 1/4 inch thick
1 pound cleaned baby spinach leaves
3 two-finger pinches Maine Coast Sea Salt (or Moroccan Atlantic Sea Salt)
3 grindings black peppercorns
2 tablespoons dry sherry
1 cup heavy cream
2 teaspoons Dijon mustard
Grating of nutmeg
2 ounces shredded Gruyere cheese
Preheat a broiler.
Heat the olive oil in a very large skillet (raw spinach occupies 50 times the space of the same spinach cooked, which means you will need a pan many times larger than you think you will need) over medium high heat. Add the mushrooms and sauté just until tender, about 4 minutes. Add the spinach leaves and stir until completely wilted, about 3 minutes. While the spinach is cooking season it with one pinch of Maine Coast sea salt and freshly ground black pepper. Transfer to a shallow gratin dish or casserole.
Return the pan to the heat and add the sherry. Bring to a boil. Add the cream and boil until the volume is reduced by half. Remove from heat and stir in the mustard and nutmeg. Pour over the spinach and spread evenly.
Scatter the gruyere on top of the spinach mixture and run under the broiler until the cheese is fully melted and preferably a little brown. If it begins to get oily before it browns remove it right away. Scatter the remaining Maine coast sea salt over top and serve immediately.