Step 1Place the shortening, 2 tablespoons sugar and the salt in a large bowl and pour the boiling water over. Stir to dissolve the sugar and salt; let stand until the shortening melts. Cool to room temperature.
Step 2Sprinkle the yeast and a pinch of sugar into one-fourth cup warm (100 to 110 degrees) water; stir and let stand until the yeast dissolves.
Step 3In the bowl of an electric mixer, combine the yeast and shortening mixtures. Add 2 1/2 cups flour and combine thoroughly.
Step 4Cover the batter and let rise in a warm place until slightly risen and spongy, about 10 minutes.
Step 5Return the batter to the mixer and add enough flour (about 2 to 2 1/4 more cups) to make a stiff dough that comes together and pulls away from the sides of the bowl. If working by hand, add the flour and beat to make a stiff dough that can be gathered into a soft, not-too-sticky ball.
Step 6Change to the dough hook attachment and knead the dough for about 5 minutes, adding more flour as necessary, until the dough is smooth and elastic. If working by hand, turn the dough out onto a lightly floured board and knead, adding flour as necessary. Fold the dough, push down hard on it, pushing away from you, then turn it a quarter turn. Fold again, push, turn. Every once in a while, pick up the dough ball and slam it down hard on the board. Knead for about 10 minutes, until the dough is smooth and elastic. Test to see if you've kneaded enough by slapping your hand on the dough, holding it there for a count of 10, then lifting up your hand. If bits of dough stick or cling to your hand, continue to knead, adding flour as needed.
Step 7Place the kneaded dough into a greased bowl, turning so that the dough is coated on all sides. Cover lightly with wax paper and let rise in a warm place free of drafts until doubled in bulk, about 2 hours.
Step 8Punch down the dough. Turn it out onto a work surface and knead half a dozen times. Let it rest for 5 minutes.
Step 9Using a sharp knife, cut the dough into plum-size pieces. Flatten each piece slightly and fold the two long sides into the middle, pressing closed the seam and twisting the ends to form a football-shaped roll. Place the rolls on a parchment-lined baking sheet, seam sides up. Cover with a piece of wax paper and let stand in a warm place until doubled in bulk, about 1 hour.
Step 10For a brown, smooth but crisp crust, heat the cornstarch and water in a small pan until thick and clear and brush on the rolls before baking.
Step 11Heat the oven to 375 degrees, placing a small cake pan on the floor of the oven to heat as the oven heats. Have ready about a dozen ice cubes. Place the rolls in the oven, then quickly and carefully place the ice cubes into the hot pan on the bottom of the oven (steam will rise immediately) and close the oven door.
Step 12Bake 30 to 35 minutes, spraying 2 or 3 times during the baking with the salt water in the plastic spray bottle. The rolls are done when they're golden brown and hollow-sounding when tapped on the bottom.