FOR THE STUFFING: Peel the fibrous outer layer of skin from the stems of the broccoli rabe; cut off and discard the bottoms of the stems if they are tough. Wash the broccoli rabe well and cut into 1/2-inch pieces.
Heat the oil in a large heavy skillet. When it is hot, add the garlic and sauté for 5 seconds, then add the broccoli, still wet from washing, along with the mushrooms and salt and pepper. Mix well, cover, and cook over medium heat for 5 minutes. The broccoli should be tender and the moisture gone from the pan. If any liquid remains, cook, uncovered, until the liquid has evaporated. Let cool to room temperature.
Meanwhile, place the monkfish fillet on the work surface and, using a long, thin, sharp knife held perpendicular to the fish and start from a long side, cut through it, stopping about 1 inch from the opposite side, so it can be opened like a book. Butterflying will create a 1/2-inch-thick rectangle about 7 inches by 9 inches. One side of the fillet will be whiter than the other; place it white side down on a work surface. Spread the cool stuffing mixture on top. Starting from a long side, roll up the monkfish to encase the filling and tie it securely with kitchen string. The finished roulade should be about 2 1/2 inches in diameter. (The roulade can be prepared up to 24 hours ahead, covered and refrigerated.)
Heat the oil and butter in a deep skillet. Sprinkle the roulade with the salt and brown it on the smooth (unseamed) side over high heat for about 1 minute. Turn the roulade over, cover, reduce the heat to medium, and cook for about 15 minutes, or until the fish is tender when pierced with a fork. Transfer the roulade to a platter.
FOR THE SAUCE: Add the wine to the drippings in the skillet and boil for 1 minute. Add the tomatoes, salt, and pepper and boil for another minute. Stir in the tarragon.
To serve, remove the string from the monkfish and cut the roulade into 8 slices, each about 3/4 inch thick. Divide the sauce among four plates and arrange 2 slices of the roulade on top, and serve immediately.
Copyright © 2011 by Jacques Pépin. Used by permission of Houghton Mifflin Harcourt. All rights reserved.
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