Boil 1 firmly packed cup dandelion greens or mustard greens in a pot of salted water until tender, about 4 minutes. Drain and cool the greens on 
a baking sheet. Squeeze out excess water, coarsely chop, and toss with 1 teaspoon extra-virgin olive oil and a pinch of cayenne pepper. Store, covered and refrigerated, up to 3 days.