Preparation

• Beat butter and flour in a bowl; spread into a 12x6-in. rectangle on waxed paper. Cover and refrigerate for at least 1 hour.
• Dissolve yeast in warm water. Add milk, sugar, egg, salt, and 2 cups flour; beat until smooth. Stir in remaining flour to form a soft dough. Turn onto floured surface; knead for 6-8 minutes. Roll into a 14-in. square.
• Remove butter from refrigerator; let stand until 55-60°. Invert onto half of dough. Fold dough over butter; seal edges.
• Roll dough into a 15x9-in. rectangle and fold into thirds. Repeat rolling and folding twice, rotating dough 90 degrees between folds. Refrigerate after folding if butter softens. Wrap and refrigerate for 2 hours.
• Mix sugar and cinnamon in a small bowl. Unwrap dough and turn onto a lightly floured surface; roll into an 18x10-in. rectangle. Sprinkle with sugar mixture. Roll up jelly-roll style from a long side; pinch seam to seal. Cut into 12 slices.
• Place in greased jumbo muffin cups, cut sides down. Cover with a towel; let rise until almost doubled, about 45 minutes.
• Bake at 375° until golden brown, 16-20 minutes. Let stand in tin for 5 minutes.
• Combine sugar and cinnamon for coating in a bowl. Toss buns in coating, shaking off excess. Let cool completely.