In a large bowl, dissolve yeast in water. Add sugar, egg, salt and 1 cup flour; beat on low for 3 minutes. Add enough remaining flour to form a soft dough. , Turn onto a floured surface; knead until smooth and elastic, about 6-8 minutes. Place in a greased bowl; turn once to grease top. Cover and let rise in a warm place until doubled, about 1 hour. , Meanwhile, in a large skillet, cook beef over medium heat until no longer pink; drain. Add cabbage, onion, salt and pepper. Cover and cook over medium heat for 15 minutes or until vegetables are tender. Stir in cheese. Remove from the heat; set aside to cool. , Punch dough down and divide into 12 pieces. Gently roll out each piece into a 5-in. circle. Top each with about 1/4 cup filling. Fold dough over filling to meet in the center; pinch edges to seal. , Place seam side down on a greased baking sheet. Cover and let rise in a warm place until doubled, about 30 minutes. Brush with butter. Bake at 350° for 20 minutes or until golden brown. Serve warm.