Finely dice the mushrooms (if using wild mushrooms with an interesting shape, cut them into long strips or wedges.) Melt 1 tb of the butter in a large non-stick skillet over medium-high heat. Add the mushrooms and onion and cook, shaking or stirring, until the mushrooms begin to wilt. Add the garlic, savory, pepper, and 1/8 ts salt. Cook until the liquid given off by the mushrooms is nearly gone, then add the sherry and cook until evaporated. Remove from heat, taste for seasoning, and set aside to cool. Remove any pin bones from the salmon fillets and season lightly with remaining salt and pepper. Lay out 2 chard leaves in opposite directions, slightly overlapping. Place a salmon fillet across the middle, skin side up (if the belly flap is especially long or thin, fold it double for a more compact, even shape.) Arrange 1/4 of the mushrooms mixture on each side of the salmon. Fold the near end of the leaves over the fish, tuck in the sides, then fold the whole thing over the remaining leaf, forming an envelope. Trim off the remainder of the leaf to form a neat package. Repeat with the remaining salmon fillet. Heat the stock and wine to a simmer in the same skillet used for the mushrooms. Place the salmon packages in the pan, seam side down, cover, and cook at a simmer until a skewer easily enters the center of the fish, 8-12 minutes depending on the thickness. Transfer the fish to plates, turn the heat under the skillet to high, and reduce the stock slightly. Swirl in the remaining butter, taste for seasoning, and pour over the fish. Per Serving: Calories: 415, Protein: 32 g, Carbohydrate: 9 g, Fat: 27 g, Saturated Fat: 11 g, Cholesterol: 125 mg, Sodium: 495 mg, Fiber : 2 g.