Combine milk and butter in small saucepan over medium-low heat; bring almost to a simmer. Remove from heat; stir in sugar and salt, cool to lukewarm. Sprinkle yeast over warm water in a large bowl, let stand 5 min. Add milk mixture, 2 cups of flour, sour cream, eggs, egg yolks, and cinnamon. Beat until smooth. Beat in enough additional flour to form a smooth, soft dough.
Turn out dough onto lightly floured surface. Knead until smooth and elastic, 8-10 minutes. Place in lightly greased bowl, turn to expose greased side. Cover with towel. Let rise in warm, draft free place until doubled. About 1 hour
It is now ready to roll out and fill with your favorite filling, cinnamon, or add dried fruit and bake.