Line baking sheet with parchment paper. Preheat oven to 375°F.

Roll out puff pastry. Cut sheet into 2- x 2-inch squares.

Shmear each square with mustard and sprinkle jalapeños on mustard. 

Pat dry hot dogs and place in the middle of the pastry, with the cut half at the bottom and end of the dog sticking out of the dough. Fold up the bottom and overlap dough to resemble a baby wrapped in blanket. 

Lay down on prepared sheet and continue wrapping remaining dogs.

Brush each dog popper with egg wash. 

Bake at 375°F for 30 minutes or until pastry is golden brown.

Serve Spicy Dog Poppers, if desired, with additional mustard.