Dissolve yeast in warm water. In a large bowl, combine hot water, sugar, salt, shortening and allow to stand until lukewarm. Add dissolved yeast and 3 cups flour. Beat until well blended. Add remaining flour. Dough will be soft. Mix with a wooden spoon and leave spoon in batter and let rest 10 min. Stir batter down to remove air. Let rest 10 min. again. Repeat this process a total of 5 times. Turn dough out on floured board and knead lightly. Divide dough in half. Roll each half into 9×12 rectangle. Roll up jelly roll style. Brush tops with beaten egg white, then sprinkle with sesame seeds. With sharp knife, slash tops about 3 times, cover and let rise until doubled in size, about 30-40 min. Bake in preheated 375ºF oven for about 30 min. or until done.