Frisee has a slightly bitter taste and crisp, curly leaves. Pair it with a tangy vinaigrette for an easy side dish.
In a blender (or screw-top jar), combine vinegar and mustard. Season with salt and pepper, and blend well to combine. Add oil, and blend until combined and thickened.
Place frisee and chives in a large serving bowl; toss with vinaigrette, and serve.
The sturdy heads of frisee will keep, bagged, for up to 5 days in the refrigerator.