If you have the time and energy to boil and clean fresh artichokes, by all means do so. Otherwise, frozen or canned artichoke bottoms will work just fine for this pizza.
Roll pizza dough into two circles large enough to cover bottom and sides of two 12″ pizza or quiche pans. Spread a tablespoon of olive oil over the bottom of each pan, then press dough circles into the pans.
Ladle 1 cup of sauce into each pan and spread evenly over the crust.
In a large, flat-bottomed wok or Dutch oven, combine washed spinach leaves, garlic, and butter. Sauté just until spinach has wilted. Remove spinach to a fine sieve and press out as much liquid as possible.
Distribute cooked spinach evenly over each pizza crust, then sprinkle artichokes evenly over the spinach.
Spread Parmesan cheese over each pizza, then do the same with the mozzarella. Add freshly ground black pepper to taste. Bake pans in a preheated oven at 400° until crust has browned and cheese is bubbly, about 20 minutes.