In a large mixing bowl, combine warm milk and sugar. Sprinkle the yeast over the top and let it sit for about 5 minutes, until it becomes frothy.
Add melted butter, salt, and eggs to the yeast mixture. Mix well. Gradually add the flour, one cup at a time, and mix until a soft dough forms.
Knead the dough on a floured surface for 5-7 minutes, until smooth and elastic. Place the dough in a greased bowl, cover it with a clean cloth, and let it rise in a warm place for about 1 hour or until it is doubled in size.
In a large skillet, cook the ground beef and chopped onion over medium heat until the beef is browned and the onion is tender. Drain any excess fat.
Add the shredded cabbage to the skillet and cook until the cabbage is wilted. Season with salt, pepper, and Worcestershire sauce (if using). Mix well. If desired, stir in shredded cheese until melted.
Preheat the oven to 375°F (190°C). Punch down the risen dough and divide it into 12 equal portions.
Roll each portion into a ball, then flatten each ball into a circle (about 6 inches in diameter). Place a generous spoonful of the filling in the center of each circle. Fold the edges of the dough over the filling, pinching them together to seal. Place the filled bierocks, seam side down, on a greased baking sheet.
Bake in the preheated oven for 20-25 minutes or until the bierocks are golden brown. Remove from the oven and let them cool slightly before serving. Recipe excerpted from Route 66 Recipes: A Culinary Cruise Along the Mother Road , reprinted with permission from Arcadia Publishing.
