Preheat oven to 400 degrees. In a small bowl, whisk together egg and 1 tablespoon water and set aside. In another small bowl, combine Parmesan cheese, mustard powder, salt and pepper, set aside.

Lightly flour your work space, and roll out thawed puff pastry sheet to a 16-by-12 inch rectangle. With the short side facing you, cut pastry sheet in half crosswise.

Brush both halves with egg wash. Sprinkle one egg washed half with cheese mixture, and sandwich the two halves together ( egg washed sides facing in). Press all sides to seal.

With the short side facing you, cut dough crosswise into 24 strips, each strip about 8 inches long and 1/2 inch wide. Place strips, 1 inch apart, onto two baking sheets. Twist each strip, pressing down the ends to ensure they don't open up.

Bake until cheese straws are golden, and dough is puffed and flaky. ( About 10 minutes).

* When twisting your cheese straws, press ends down to adhere them to the e baking sheet so they don't flare up while in the oven.