1. Preheat oven to 400 degrees. Unfold pastry on a work surface. Using a pizza cutter or knife, cut pastry into 10 equal strips; cut each strip crosswise into thirds (to yield 30 1-by-3-inch pieces). Wrap a strip of pastry around each frank, and place, seam side down, 2 inches apart on a rimmed baking sheet.

2. Brush top of pastry with egg; sprinkle with poppy seeds. Bake until golden, 25 to 30 minutes. Serve with ketchup.