Ingredients
1 tablespoon butter2 cups finely chopped fresh mushrooms1 small onion, finely chopped1 package (15 ounces) refrigerated beef roast au jus1 large egg1 tablespoon water1 package (17.3 ounces) frozen puff pastry, thawed6 slices provolone cheese
Preparation
Preheat oven to 425°. In a large skillet, heat butter over medium-high heat. Add mushrooms and onion; cook and stir 5-7 minutes or until tender and liquid is evaporated. Remove from pan; cool completely.
Drain beef, discarding sauce or saving for another use. Coarsely chop beef. In a small bowl, whisk egg and water.
Unfold one sheet of puff pastry. On a lightly floured surface, roll pastry into a 15x9-in. rectangle; cut crosswise into thirds, making three 5-in.-wide rectangles.
Place a cheese slice on one half of each rectangle, trimming cheese to fit. Top each with a rounded tablespoon mushroom mixture and scant 3 tablespoons beef. Lightly brush edges of pastry with egg mixture. Fold pastry over filling; press edges with a fork to seal. Transfer to a parchment-lined baking sheet. Repeat with remaining pastry sheet and filling.
Brush tops with egg mixture. Bake 17-20 minutes or until golden brown. Serve warm.
