Wash greens and shake dry, allowing some water to cling to leaves. Cut into rough sections, 3 or 4 inches long; cut off and discard any stems thicker than 1/4 inch.
Put greens in a deep skillet that can be covered, along with wine, garlic, half the butter, and some salt and pepper. Turnheat to medium-high, cover and cook, checking occasionally tomake sure mixture does not dry out, until greens are justabout tender, 10 minutes or so.
Put fish on top of greens, season with salt and pepper, and dot with remaining butter. Re-cover, and cook until fish is done and greens fully tender, 5 to 10 minutes more.