This stuffed bread loaf, loosely based on the vegetable and meat mixtures found in Italy, is tasty either hot or at room temperature. Use a tube of refrigerated pizza dough to save time.
Preheat oven to 400° F.
Heat 1 and ½ tablespoons of the olive oil in a large frying pan. Add the garlic and onion and cook, stirring frequently, for 2 minutes. Stir in the spinach, celery, ham (if using), and pepper. Continue cooking for 5 minutes, stirring frequently, or until the spinach is wilted. Add the mushrooms and olives, and cook 2 minutes longer, stirring constantly.
Scrape the mixture into a colander set over a bowl to cool.
Roll out the dough to a 10x12-inch rectangle. (The dough should be about ½ inch thick.) Oil the surface with the remaining ½ tablespoon olive oil.
Cover the dough to within an inch of the edges with the filling. Sprinkle with the grated cheeses.
With the longest edge parallel to you, roll up the dough like a jelly roll, tuck the ends under, and place it diagonally, seam side down, on a greased cookie sheet. Cut two deep slashes in the top to allow steam to escape.
Immediately bake for 40 to 50 minutes, or until the bread is cooked through and the top is golden brown. Cool thoroughly before cutting into slices.