1. In the bowl of an electric mixer combine warm milk, butter and sugar. Sprinkle yeast on top and let stand 2 min until yeast softens. With the bread hook attachment stir in the egg, salt, and 3 cups of the flour. Mix well, then add remaining flour and mix until dough pulls away from the bowl edges, about 5 min.
2. With floured hands form dough into a ball and place in a buttered bowl, turning to coat all sides of ball. Cover bowl with plastic wrap and let dough rise in a very warm place until doubled in size, about 3 hr.
3. Make filling by combining the sugars, cinnamon, and chocolate. Butter two 8-by-8-inch pans and set aside.
4. Turn dough onto a lightly floured work surface and roll into a 14-by-24-inch rectangle about 1/8 inch thick. Spread with the melted butter and sprinkle with the cinnamon mixture. Starting with one long end, roll dough tightly to form a long spiral. Pinch the seam together. Cut into 18 slices, about 11/4inch thick each, and place 9 in each prepared pan. Cover with plastic wrap and refrigerate overnight.
5. In the morning remove rolls from refrigerator and bring to room temperature in a warm place, 1 hr. Heat oven to 375 degrees F and bake until rolls are golden and cooked through, 18 to 20 min.
6. Let rolls cool slightly then spoon on some Vanilla Icing. Serve warm. Makes 18 rolls