Reinhart says you can add toppings as well, although I haven't. He suggests adding most things after removing the dough from the fridge, so that they can be nestled safely by the dough and won't fall off. Anything moist should be sauteed first to remove excess moisture. The exceptions are perishable items, such as meat and high-moisture cheese, which should be added right before baking. Dry cheese can be added after the 15-minute mark and baked for another 5 minutes.