I have written frequently about annual arugula and how delicious, versatile, and easy it is. A few years ago I bought a packet of seed for perennial arugula, Diplotaxis tenuifolia. I planted them in a likely spot and then, as so often happens at my place, I was overcome by the sight of bare earth, forgot I had sown seeds already, and planted something large and rambunctious there. At the end of the gardening year I cleared the debris away and found tiny wispy plants that I recognized as the perennial arugula. They survived the winter, resprouted tentatively in the spring, and then all of a sudden they were a mass. A thuggish mass, ready to overpower anything in the way of their gangland fervor for territory. And they were, literally, hot. The initial flavor when I chewed on a leaf was pleasantly mustardy, developing gradually to a burn in the back of the throat as I swallowed that wasn’t painful, but certainly wasn’t pleasant either. While I puzzled over how to use them, they bloomed, and the delicately pretty sulfur-yellow blossoms drew bees from miles around. So, needless to say, they were kept.
Sometimes it takes me a while to find the best use for a perennial. So far, my favorite use for this sturdy perennial is to blanch the leaves briefly in boiling water and use them more as a seasoning than a bulk ingredient. Used as a small part of a cooked greens mixture, they add interest. I like a small buttered pile of them as a sort of “cooked herb salad” alongside meats or salmon. I intend to try pounding them with a mortar and pestle as a wasabi-like seasoning. And they are superb in Montpellier Butter. I learned about this lovely seasoning in one of Elizabeth David’s books, I forget which one. But the greatest recipe of them all is the one published by Jeremiah Tower, and it goes like this:
Jeremiah Tower’s Montpelier Butter (this is as he published it. My own tweaks are below.)
6 spinach leaves, washed
2 shallots, finely chopped
1/2 bunch watercress leaves (I use 15 good-sized nasturtium leaves)
2 tablespoons fresh flat-leaf parsley leaves
2 tablespoons fresh chervil leaves
2 tablespoons chopped fresh chives
1 tablespoon fresh tarragon leaves
2 cornichons, rinsed and chopped
4 salted anchovy fillets, rinsed, soaked in water for 10 minutes and dried with a paper towel
2 tablespoons salted capers, rinsed, soaked, and drained
1 small garlic clove
1/4 teaspoon cayenne pepper
Freshly ground black pepper
3 hard-cooked large egg yolks
2 large raw egg yolks
1/2 cup (one quarter pound) good grassfed butter, room temperature
1/2 cup extra-virgin olive oil
1 teaspoon white-wine vinegar
Bring a large saucepan of water to a boil; add salt. Combine spinach, shallots, watercress, parsley, chervil, chives, and tarragon in a fine sieve. Carefully place sieve in boiling water until greens are wilted, about 30 seconds. Remove, and place in ice-water bath to cool, or hold under very cold running water for several seconds until cool. Remove, and squeeze dry. Transfer to the food processor. Add cornichons, anchovies, capers, garlic, and cayenne pepper. Season with salt and black pepper. Process to a smooth paste. Add cooked and raw yolks, and butter. Process until thoroughly combined. Transfer to a medium bowl and slowly whisk in olive oil. Add vinegar, and whisk to combine. Adjust seasoning, if necessary.
This will keep a day or two in the refrigerator, and two months in the freezer.
My tweaks: I leave out the spinach leaves, watercress or nasturtium leaves, and chervil, and use about 25 perennial arugula leaves instead, blanched with the other seasonings as described above. I increase the tarragon to a quarter cup of whole leaves, and I also use a few large cloves of confited garlic rather than one raw clove. I use five hard-cooked egg yolks so that I don’t have to worry about harming an immunocompromised guest. And sorry, Jeremiah, but I do the whole thing in the processor and don’t whisk by hand at the end. I keep the butter in roughly formed little bars in the freezer, tightly wrapped, so that I can cut off large (LARGE) pats with a heated knife and plop them on steaks or grilled salmon and heat briefly under the broiler just before serving to soften and partially melt the butter, or on steamed vegetables, or on nearly anything. I don’t eat the carb-y stuff anymore, but if you do, it is wonderful on chunks of grilled baguette and transcendent on handmade egg linguine with grated Parmesan. If you try this with frozen Montpellier butter and don’t want to take time to thaw it, try grating it on a coarse grater before tossing with the linguine, piling on the salmon, or adding generously to the cooked greens.