Sauté leeks in butter in a medium skillet over medium heat about 5 minutes or until softened. Stir in garlic, and cook 1 minute. Add wine; cook 5 minutes or until liquid evaporates. Remove from heat, and stir in lemon zest, 1/4 teaspoon salt, and 1/8 teaspoon pepper.
Roll out each pastry sheet on a lightly floured surface into a 12-inch square. Cut each in half, forming 4 (12- x 6-inch) rectangles. Spoon 1/4 cup leek mixture lengthwise down the center of each rectangle. Sprinkle fillets evenly with remaining 1/4 teaspoon salt and remaining 1/8 teaspoon pepper; place fillets lengthwise on top of leek mixture. Fold short sides of pastry over fillets. Pinch together long sides of each pastry to seal. Place Wellingtons, seam-side down, on an ungreased baking sheet.
Bake at 425° for 18 to 20 minutes or until pastry is golden brown. Let stand 5 minutes. Cut each pastry diagonally in half using a serrated knife.
Wines: We suggest the 2006 Lumiére Chardonnay from Sparkman Cellars. Owner and winemaker Christian Sparkman says it's perfect for this classic salmon preparation, with the acidity and body to enhance the fish's rich flavors. Seeing red? Mark Ryan's 2006 Black Love Pinot Noir is spicy and silky.