• Preheat the oven to 425 degrees. If you have one, place a pizza stone in the oven.

Make the dough

• Combine the yeast and sugar in the warm water in a bowl. Add the warm water. Stir to dissolve and let stand for 10 minutes. (This 10 minutes is a good time to put together the filling.)
• When the 10 minutes have elapsed, insert the blade attachment into your food processor. Combine the flour and salt to the bowl of the processor.
• With the food processor running, pour the yeast mixture through the feed tube and process for about 45 seconds, until the dough begins to gather into small balls.
• Add the oil through the feed tube and process for about 60 more seconds. If the dough isn't forming a ball, add a tablespoon or two or water and continue to process.
• Remove the ball of dough from the food processor bowl. For single serve calzones, divide the dough into four equal parts.

Make the filling

• In a medium size bowl, mix together the ricotta, mozzarella cheese and chopped spinach. Season with salt and pepper, if desired.

Make the calzones

• Roll out each of the dough pieces on a floured surface into a rough circle.
• Scoop a quarter of the filling onto one side of the dough circle.
• Fold over the top of the circle to close the calzone. Seal the calzone closed, using a bit of water if necessary.
• Repeat with the other 3 pieces of dough and remaining filling.
• Transfer the calzones to the baking stone or a cookie sheet. Bake for 12 to 15 minutes, or until golden brown.
• Serve with warmed tomato sauce.