Bake 4 of the hot dogs on a baking sheet for 5 mins. Let cool to room temperature.
Unfold defrosted puff pastry on floured board. Cut sheet into 4 equal pieces crosswise and brush with 1 tsp mustard. Place one hot dog on each piece of puff pastry over the mustard. Add some drained sauerkraut if desired to each dog. Wrap tightly, overlapping at end by 1/2". Seal it by brushing with water, and cut off excess pastry if any. Repeat with the remaining hot dogs and puff pastry.
Place each roll seam side down on a parchment-lined baking sheet. Brush with egg wash. Score puff pastry into 7 equal pieces on the diagonal. Bake for 20-25 minutes, until browned. Serve immediately with more mustard and sauerkraut if you wish.