In a large bowl, dissolve yeast and 1/2 teaspoon sugar in 1/4 cup water; let stand for 5 minutes. Beat in the egg yolks, remaining sugar and water.
Combine the flour, milk powder and salt; cut in butter until mixture resembles coarse crumbs. Gradually add to yeast mixture to make a soft dough. Place in a greased bowl, turning once to grease top; cover and refrigerate overnight.
Turn dough onto a lightly floured surface. Cover with a kitchen towel; let rest 10 minutes. Roll into an 18x10-in. rectangle; spread with softened butter. Combine sugar and cinnamon; sprinkle over butter. Roll up jelly-roll style, starting with a long side. Pinch edges to seal. Cut into 3/4-in. slices.
Preheat oven to 350°. Combine topping ingredients; sprinkle some on waxed paper. Place slices, cut side down, on cinnamon-sugar; roll each into a 5-in. circle, turning to coat both sides and adding cinnamon-sugar as needed. Place 2 in. apart on greased baking sheets. Sprinkle tops with leftover cinnamon-sugar if desired. Bake 15-20 minutes or until golden brown. Remove from pans to cool on wire racks. Make about 2 dozen.