Savory Truffle Strudel

Heat the oven to 400°F.  Beat the egg and water in a small bowl with a fork or whisk.
Gather filling choices and combine in a bowl.
Unfold the pastry sheet on a lightly floured surface. Roll the pastry sheet into a 16×12-inch rectangle. With the short side facing you, spoon the filling mixture onto the bottom half of the pastry sheet to within 1 inch of the edge. Starting at the short side, roll up like a jelly roll. Tuck the ends under to seal. Place seam-side down onto a baking sheet. Brush with the egg mixture.
Bake for 25 minutes or until the pastry is golden brown.  Have a drink.
Remove the pastry from the baking sheet and let cool on a wire rack for 10 minutes.