Preheat oven to 400°F. Place pastry on a sheet of wax paper; sprinkle evenly with 1/3 cup Parmesan; top with another sheet of wax paper. Using a rolling pin, roll out pastry slightly, flip pastry over, peel off paper and sprinkle evenly with another 1/3 cup cheese. Cover with wax paper; roll out into a 12-by-10-inch rectangle. Remove wax paper. Cut dough lengthwise into 24 strips. Shape each into a 2 1/2 -inch pretzel; arrange on 2 greased baking sheets.
Brush dough with egg yolk; sprinkle with remaining 1/3 cup cheese. Bake until golden, rotating pans once, 12 minutes. Serve with mustard for dipping.