Meanwhile, put the ricotta cheese and the spinach leaves in a blender and blend at high speed until you have a smooth, bright green mixture. Sift the flour into a bowl with the salt. Make a depression in the center of the flour and add 3 tablespoons of the oil, the egg, the spinach mixture and the yeast mixture. Put flour on the kneading board and place the dough mixture on the flour. Knead the mixture for 8 to 10 minutes until the dough is uniformly mixed and elastic. Add flour as you knead if necessary to keep the dough from becoming too sticky.
When the dough is ready, place it in a clean bowl that has been brushed with oil. Brush the top of the dough with oil and place a clean cloth over the bowl. Put the bowl in a warm, draft-free place for 11/2 hours.
This recipe will make:
2 thin crust pizzas, 12-inches each
2 stuffed pizza pockets
1 thick crust pizza, 14-inch
6 - 6-inch pizzas