1 bunch spinach, about 3/4 pound
1/4 cup olive oil
1 pound mushrooms, thinly sliced
1/2 medium-size red onion, chopped
2 medium-size cloves garlic
3/4 cup part skim ricotta cheese
2 tablespoons grated Parmesan cheese
3 tablespoons chopped parsley
1/4 teaspoon dried thyme
1/8 teaspoon ground nutmeg
salt, to taste
freshly ground pepper, to taste
Stem and rinse the spinach. Drain in a colander but do not spin dry.
Heat 2 tablespoons oil in a large frying pan over high heat. Add half of the mushrooms and cook, stirring, for 3 to 4 minutes until lightly browned and tender. Add half of the onion and cook for 1 minute. Lower the heat if the vegetables begin to burn but don't let any liquid accumulate in the pan. Add half of the garlic and stir for 30 seconds. Transfer the mixture to a bowl. Repeat with the remaining oil, mushrooms, onion and garlic.
Decrease the heat to medium. Add the spinach with just the water that clings to the leaves. (If the spinach is very dry, add 2 to 3 tablespoons water.) Cover and cook for about 5 minutes until wilted, Drain the spinach in a colander and squeeze out the water. Chop the spinach and add it to the bowl with the other vegetables. Add the cheeses, parsley, thyme, nutmeg and salt and pepper to taste. Stir to combine.
Heat the oven to 500 degrees. Oil 2 baking sheets and sprinkle lightly with cornmeal. Divide the dough into 4 equal pieces on a lighty floured work surface. Shape each into a ball and flatten each ball into a 7- to 8-inch round. Spread a quarter of the filling over one half of one dough round. Fold the remaining half over the filling to form a semicircle and fold the bottom edges over the top to seal. Transfer to a baking sheet. Repeat with the remaining dough rounds and filling. Bake the calzone for about 10 minutes until the crusts are golden brown.