Separate stems and leaves from 1 bunch cilantro (you should have about 1/2 cup of each); coarsely chop leaves. Purée cilantro stems, 1/2 cup sour cream, 1 teaspoon finely grated lime zest, and 3 tablespoons fresh lime juice in a blender.
Transfer cilantro mixture to a large bowl and whisk in 1/2 cup mayonnaise; season with salt and pepper. Toss in 1/4 very thinly sliced large head of green cabbage (about 5 cups), 1 julienned peeled small jicama (about 1 cup), 4 sliced scallions, and chopped cilantro leaves. |