Bring a large pot of water to a boil; salt it. Meanwhile, if the collard stems are more than 1/8 inch thick, separate them from the greens. Roughly chop both stems and greens.
If the stems are thick, place them in the water first. After 5 minutes, add the leaves. Cook until the stems are tender enough to pierce with a thin‐bladed knife, from 5 to 15 minutes depending on their thickness.
Drain and serve immediately, or plunge into an ice‐water bath and drain. Reheat according to the directions for Precooked Vegetables in Butter or Oil.
Serve hot greens with butter, extra‐virgin olive oil, and/or lemon juice or vinegar.