Prepare the Perfect Yeast Pastry Dough recipe as instructed, but reduce the sugar to one tablespoon to keep the dough savory. Heat a large skillet over medium-high heat. Add the ground beef and diced onion, breaking the beef apart as it cooks. Sauté until the beef is browned and the onions are tender, about 12–15 minutes. Reduce the heat to medium.
Add the shredded cabbage and continue cooking until the cabbage is tender. Season the mixture to taste with salt and pepper, then stir in the shredded cheese.
Line two baking sheets with parchment paper. After the dough is done rising, gently deflate it, transfer it to a floured surface, and divide it into 16 equal pieces (about 90g each). Shape the pieces into balls, cover them with a towel, and set them aside.
Roll each dough ball into an 6-inch round, thinning the edges slightly. If the dough recoils, allow it to rest for 5 minutes. Add 1/2 cup of filling in the center, leaving a 1-inch border.
Gather and pleat the dough over the filling, pinching to seal. Twist the top, then press gently to flatten the seam.
Place the bierocks seam-side down on the parchment lined baking sheets, leaving a few inches of space between each one.
Preheat the oven to 350°F. Allow the bierocks to rest for 30 minutes until they are puffy. Whisk together the egg and water, then brush each pastry with the egg wash.
Bake the bierocks for 30-35 minutes, rotating halfway through, until they are golden brown. Cool them on a wire rack for 5 minutes, then serve with mustard or your choice of condiments. Enjoy!