My girlfriend, Kate, is an editor and writer who focuses on health and medical news, and she loves to tell me when a food I like happens to be extra healthy. (She also, very often, likes to tell me when my diet is unacceptably unhealthy.) Take watercress, for example. Every time I say how much I love it, she says, "It's really, really good for you, too." That's good to know, but honestly, it's not why I love watercress so much. No, for me it's the peppery bite and those wonderfully plump-crisp stems. And, unlike a lot of other tender leafy greens used to make salad, watercress is incredibly forgiving, tasting just as good slightly wilted—and even fully cooked—as it does raw. I love it so much, in fact, that it's one of my go-to greens when I want to turn a salad into a full meal...that just happens to be really healthy, according to Kate.
The trick to getting the best results, I find, is taming watercress's punch with the other ingredients in the salad. Often, that means I dice up an avocado and add it to the mix, its rich, buttery oils helping to offset some of that pungency. This time, though, I went with something even more robust: pan-roasted oyster mushrooms. They're earthy and hearty, which not only balances out those bitter and peppery cress flavors, but also adds a meatiness that turns this into a complete and satisfying dinner.
Making it is easy enough. First, I sear the mushrooms in a skillet until they're tender and lightly browned, working in batches and over high heat so they color quickly instead of just steaming. Though I really like oyster mushrooms in this salad, you can substitute other types according to what's available. King oyster mushrooms sliced into slabs would be great, as would hen-of-the-woods, chanterelles, or even plain old creminis.
As each pan of mushrooms finishes, I transfer them to a baking sheet and spread them in an even layer to cool. This is a great way to cool anything quickly—increasing surface area allows the heat to escape much more rapidly. Aluminum baking sheets are also extremely conductive of heat, which means that they transfer heat more rapidly from the mushrooms to the air in your kitchen.
Once the mushrooms are at room temperature, I toss them in a salad bowl with the cress and plenty of shaved Parmigiano-Reggiano or Grana Padano to double down on the savory flavor. The cheese also helps make the salad more filling by delivering extra fat and protein, which is pretty much the only way a salad can work as a meal for me.
Then I toss it all with a tarragon vinaigrette, which I make by starting with Kenji's basic vinaigrette and adding fresh tarragon. In Kenji's original recipe, he calls for whisking or shaking the vinaigrette together, but I use an immersion blender to mince the tarragon more finely and blend it more fully into the vinegar base. Still, I'm careful not to use the blender when adding the olive oil, since that can make the oil very bitter.
Don't even think about how healthy it is if you don't want. There's more than enough flavor to focus on here.