Cut four 4-ounce bratwurst or knockwurst sausages into 6 rounds each. Stretch 1/2 pound pizza dough into a 6-by-12-inch rectangle; cut crosswise into 12 strips, then cut each strip in half. Wrap each strip around a sausage round and place on a parchment-lined baking sheet; brush the dough with beaten egg and sprinkle with poppy seeds. Bake at 400 degrees F until golden brown, 12 to 15 minutes. Serve with mustard.