I'm of 100% Volga German descent (my great-grandparents settled in
Ellis County, Kansas, so let me expound on this.
You don't need to create a recipe for Runza, or as we call them, Bierock; there are many in cookbooks and even on the Internet. If the bread is too sweet, reduce the sugar to 1/4 cup and use 1 tsp salt. As far as the filling is concerned, traditionally it is meat, cabbage or sauerkraut, onion, salt, and ground black pepper, and I sometimes make Bierock that way.
But then, this turnover lends itself well to innovation. I'm not fond of cheese in them, as the Runza restaurants offer, but I sometimes use all ground beef, 2/3 ground beef and 1/3 ground pork; fresh, mildly seasoned country sausage; or even chopped ham. The cabbage is best finely shredded (like sauerkraut). Saute the cabbage with the meat until the cabbage is no longer crisp (if using sauerkraut, drain it well before adding to the sauteed meat and saute until most of the moisture is cooked off). Add a lot of chopped onion and even some finely minced garlic onion if you prefer toward the end of the cooking period. Sometimes I add a generous pinch or two of caraway seed with the onion. Season with more salt if needed and lots of ground black pepper.
Now for a shameless plug: For a great cookbook of German Russian (Volga German, Black Sea and Bessarabian German, and Russian Mennonite) recipes, Sei Unser Gast (Be Our Guest) go to http://www.northstarchapter.org .