Soften yeast in the warm water. Set aside. Combine rye flour, molasses, shortning, salt and boiling water. Blend well. Cool to lukewarm. Add softened yeast. Gradually stir in white flour to make a soft dough, mixing well. Turn out on a well floured surface. Cover and let rest 10 minutes. Place in lightly greased bowl, turning to grease surface. Cover and let rise until almost doubled, about 30 minutes. Turn out on lightly floured surface and divide into 4 equal parts. Form into balls and cover. Let rest 15 minutes. Form into loaves. Let rise until almost double, about 1 hour. Brush with slightly beaten egg. Bake @ 350 for 35-40 minutes.