In order to become palatable, rhubarb needs to be sweetened. But how — and to what degree — you sweeten it makes all the difference in how you experience this unusual-tasting vegetable. It has three sides to its nature — one that leans toward celery and green bell pepper, another that suggests the brightness of berries, and a third that brings to mind the fresh juice of an apple.
I was playing around with a few stalks of rhubarb the other day, trying to fashion it into a garnish for grilled leg of lamb, and came up with a technique and a supplemental ingredient that worked quite well. I think it was the best rhubarb I had ever eaten. (Forgive this egregious immodesty; let me countermand it by pointing out the lamb came off the grill black on the surface and raw in the center.)
The technique was a basic gastrique, or classical French fruit sauce. The foundation of this sauce is dark, caramelized sugar. Once the sugar reaches this stage, you deglaze it with vinegar and/or fruit juice, which raised a great fuss, and then let the mixture caramelize again.
This technique gives the sauce a sweet-sour underpinning that your palate must search for to recognize. Unlike other sweet-and-sour sauces that can be so flashy and vulgar, a gastrique has the unmistakable flavor of elegance. Then you typically add pieces of fruit, stock and a little butter to finish.
As I was aiming for more of a chutney than a sauce, I made some adjustments and came upon the idea of finishing the mixture with a glug of mirin — the sweetened sake that is indispensable to Japanese food.
Once the mixture cooled, I ended up with a rhubarb compote that tasted neither sweet nor savory, but someone poised between the two. The berry flavor was bright but not brassy, and its vegetable essence didn’t struggle with the sugar. This was rhubarb I could see tasting right not only with lamb or duck, but also with yogurt or ice cream, with poached chicken, with avocados and fromage blanc, or (seriously) with sashimi or beef carpaccio.
I’ve only made it once without measurements, so please only consider the recipe below if you’re comfortable adjusting to taste.
Cut the rhubarb into 1/2 inch cross sections and set aside. Place the sugar in the center of a large, heavy-bottomed pan or pot (I used a cast-iron Dutch oven) with about 2 tablespoons water poured over the top. Heat over a medium-high flame and stir just enough to break up any clumps of sugar. Let the sugar reach a medium-dark caramel. Add the vinegar (carefully — it may splash) and stir. Don’t worry about breaking up the caramel if it seizes. Add the oil and rhubarb and stir to coat. It should be sizzling a bit. Add the salt and mirin and stir carefully to fully deglaze the pan and reduce the mirin. Cook, stirring constantly, until a few pieces of rhubarb begin to break apart. At that moment, carefully transfer the fruit and the juices to a bowl and chill.