Put butter, salt and sugar in mixing bowl. Add milk. When lukewarm add dissolved yeast cake, white of egg, and flour, reserving one-half cup. Knead until smooth and elastic; cover and set to rise until light, then shape first in small balls, then roll on the board (without flour) with the hands until about seven inches in length, using care that they are of a uniform size, rounding the ends. They should be about the size of a lead pencil. Cover and let rise. Just before putting them in the oven, brush them over lightly with melted butter and sprinkle them with salt. Bake in a slow oven, browning them delicately.