Step 1

Preheat oven to 425°F. On a lightly floured surface, roll 1 puff pastry dough sheet into a 12- by 14-inch rectangle. Cut rectangle in half lengthwise, then cut each half into 3 equal pieces for a total of 6 pastry pieces. Repeat with second pastry.

Step 2

Pat hot dogs dry with paper towels and pierce each several times with a fork. In a small bowl, whisk together egg and salt for egg wash. Roll each hot dog in 1 puff pastry piece, then seal with some egg wash.

Step 3

Place pastry-wrapped hot dogs on parchment-lined baking sheets and lightly brush with remaining egg wash; sprinkle with poppy seeds. Bake until puffed and golden, about 20 minutes. Slice each pastry-wrapped hot dog into 5 sections and serve warm with spicy mustard, if desired.