1. In a large mixer bowl, whisk the yeast with the water and let stand two to three minutes.
2. Add the milk or water and oil or shortening. Let the mixture cool a bit and then add the sugar, salt, eggs and yolks. Stir well and pour into the yeast mixture.
3. Add the flour and stir on low speed to form a soft dough. Increase the mixer speed to medium and knead for five to eight minutes, adding a bit of flour as needed to form a firmer dough. When the dough is smooth and elastic, remove the dough hook, spray the dough with nonstick cooking spray and cover the bowl with a large plastic bag. Let the dough rise until almost double in size or do a cold rise overnight in the refrigerator.