Preheat oven to 400˚F. On a lightly floured surface, take 1 sheet puff pastry and, using a rolling pin, carefully roll out the dough so it is just large enough to fit into a 9-by-13 inch pan with ½-inch overhang. Transfer to the refrigerator.
In a large skillet over medium heat, cook butter, bacon and onion for 10-
Stir in mayonnaise, ketchup, and relish. Stir in 2 eggs. Evenly spread meat mixture onto prepared puff pastry sheet. Layer tomato slices followed by cheese over the beef.
Roll out remaining sheet puff pastry to 9-by-13-inches and arrange over pie. Fold edges of bottom sheet of dough over top sheet and pinch to seal. In a small bowl, whisk remaining egg and 2 tablespoons water to make an egg wash. Brush top of pie with egg wash and transfer to oven to bake for 25-30 minutes, until puffed and golden brown. Cool for 10 minutes before serving.