To Make Dough: In a large bowl, mix together milk and oil. Stir in eggs, yeast, sugar, salt and 5 cups of flour. Mix well adding remaining cup of flour as necessary to form kneadable dough. Knead for a few minutes, then cover bowl and let dough rise one hour in a warm place.
To Make Filling: Brown beef in a large saucepan; do not drain juices. Add onion and cabbage to skillet and continue cooking until onion is soft; add salt and pepper to taste. Let cool.
After dough has risen, roll out hunks of dough (about the size of tennis balls) as thin as possible. Place 1/2 slice of cheese on dough, top with filling, then place other 1/2 of cheese on top of filling. Fold over and seal like a turnover (moistening edges with water may help seal them). Place on a baking sheet, brush with egg wash and, if desired, sprinkle with sesame seeds.
Bake in a preheated 350 degrees F (175 degrees C) oven for 30 minutes or until golden brown. Serve immediately or cool and freeze for later. To reheat frozen bierrocks simply bake until hot.