Cream together 1/4 cup sugar, cream cheese and egg yolks. Cut crusts from bread. Flatten bread with a rolling pin until thin. Mix 12 tablespoons sugar and cinnamon. Spread 1 tablespoon of cream cheese mixture on bread. Roll-up. Repeat this process, until all bread sliced are filled with cream cheese mixture and rolled-up. Working with 1 roll-up at a time, brush with melted butter and roll in cinnamon sugar. Cut in halve or thirds. These may be frozen at this point or bake for 10 minutes at 400 degrees F. To serve, guests should dip roll-ups in sour cream. Swirl just a touch cinnamon in the sour cream, if desired.