In a large bowl, dissolve yeast in the 3 1/2 cups warm water.
Add 3 cups flour and the shortening, salt and sugar.
Beat with an electric mixer for 2 minutes, then add the rest of the flour, beating until all flour is incorporated and a sticky dough ball is formed.
Turn out onto a floured surface, putting a little bit more flour on the top to prevent sticking.
Knead for about 7 minutes, adding as little flour as possible, but enough to prevent it from sticking.
Allow the dough to rest for 5 minutes before transferring to a well-greased bowl.
Turn the dough over in the bowl once to get it coated.
Cover lightly with a clean kitchen towel and let rise for at least two hours.
Punch dough down.
Divide dough in half.
On a lightly floured surface and with floured hands, gently form it into a ball and place on a sheet of parchment. Do the same with the second half.
Let both loaves rest for 40 minutes.
Place a pizza stone in the oven on the middle shelf. On the lower rack, place the broiler pan or another metal pan. You will use this to hold the water during baking.
Preheat to 450° F. If you do not have a pizza stone, you can also use a rimmed baking sheet turned upside down - see note*. Allow the stone to sit in the oven for 20 minutes at 450° F before placing the dough on top of it. If using a baking sheet, only place it into the oven for 10 minutes prior to baking, not the 20 as with the pizza stone.
Lightly dust the top of the first loaf with flour and then, with a sharp knife, score an X into the top.
Place the dough with the parchment onto the pizza stone or upside down baking sheet in the oven.
Pour the one cup of water into the broiler pan. Quickly shut the oven door to contain the steam.
Bake for 24 - 28 minutes, until golden brown.
Do the same with the second loaf.
The loaves can be tested for doneness by tapping on the bottom. They should sound hollow.
This recipe makes two loaves. Instead of using the dry yeast from a jar, you can also use 1 package of dry yeast which will yield you the amount needed. For rising, I usually turn my oven to the lowest temperature and then turn it off before I place the dough into the oven to rise.