Of all the recipes in this book (and, of course, this statement is made prior to publication) this is the numero uno so far, in terms of repeat requests and general all-round joyous reception it gets at home. (I concede that since my on-hand sample demographic is the teenage market, factors are skewed in its favor.) It amuses. But then, a culinary pun, it is intended to amuse: it looks like a pizza, but its base is made out of meatball mixture, moreover a meatball mixture you don't have to roll into balls but can simply press into a pan, rather like a juicy disc of meatloaf, or polpettone. I first came across this idea in the form of Giuliano Hazan's Meat Pie Pizza Style (though mine is a characteristically lazy, simplified version) in his book Every Night Italian, but it was the great Ed Victor, consumer of bonnes bouches and producer of bons mots (if you'll forgive my French) who named it Meatzza. I have been struggling with the problem of conveying this particular pun in Italian, and the best I can come up with (so far) is polpettizza but maybe this isn't a particularly Italian joke, anyway. Quite rightly, Italians take their traditions seriously, but I am untroubled and hope they will be, as this is seriously delicious. What's more, I find it more and more helpful in the repertoire as so many children-small children at any rate-seem to be kept on strict wheat-free diets by their parents these days; this is why I've given the option of replacing the bread crumbs with oatmeal, and very well it works, too. All in all, it is just about the perfect children's supper. My own children favor a Meatzza Margherita so I've kept it simple, but of course you could add any other toppings you like.
In a large bowl, using your hands, combine the beef, Parmesan, breadcrumbs or oatmeal, parsley and eggs. Grate in (or mince and add) the garlic and add some salt and pepper. Do not overwork it, just lightly mix together, or the meat will become compacted and dense.
Butter a shallow, round baking pan of about 11 inches diameter and turn the meat into it, pressing the mixture lightly with your fingers to cover the bottom as if the seasoned ground meat were your pizza crust.
Make sure you've drained as much runny liquid as possible out of your can of diced tomatoes, then mix the tomato with the garlic-flavored oil, oregano and some salt and pepper, and spread, using a rubber spatula, lightly on top of the meat base. Arrange the mozzarella slices on top, and then put in the oven for 20 to 25 minutes, by which time the meat should be cooked through and lightly set and the mozzarella melted.
Remove from the oven and let it sit for 5 minutes, then adorn with some basil leaves and bring it to the table before cutting into wedges, like a pizza.