Mix parmesan and oregano in a small bowl. Set aside. Prepare dough. Divide into 6 equal portions. Place two portions in a quart sized zip top bag and freeze for later use. Cover remaining portions loosely with foil and set aside. Heat oil in a large skillet. Add onion. Cook until translucent, about 4 minutes. Add tomatoes, olives, artichokes, and spinach. Cook until spinach wilts, about 4 minutes. Remove from heat and stir in cheese, salt, and pepper. Working with one dough portion at a time, roll into a 8 inch circle (or thereabout). Fill 1/2 the circle with about 1/3 c. (heaping) spinach mixture. Fold the other half over the filling, and pinch edges to seal. Place calzone on parchment-lined baking sheet. Repeat with remaining dough portions and remaining filling. Mix egg yolk and water. Using a pastry brush, brush the tops of the calzones with the egg wash. Sprinkle with the parmesan mixture. Bake at 400 for about 10 minutes, or until golden brown.