Dissolve the yeast in a little warm milk and add to the flour. Gradually add enough water to give the mixture sufficient consistency. Add the remaining milk and the sugar gradually and the sticks of cinnamon, and put in a saucepan on a slow fire. Stir vigorously and continuously till the mixture thickens. Remove from the fire and, when cold, shape into small balls and fry in the hot butter. Sprinkle with crushed crystallized sugar before serving.