Split bread lengthwise then cut in half again and hollow out some of the insides of bread. Lightly crisp bread in oven, 5 to 8 minutes. Remove bread and switch broiler on.
Heat a nonstick skillet over medium-high to high heat. Add extra-virgin olive oil, 1 turn of the pan. Add the pancetta, render a minute or so, add the meat and break it up into an even layer. Let the meat caramelize 1 to 2 minutes without stirring. Break it into small bits and brown well. Add garlic, onions and carrots and season with lots of coarse pepper, some salt, Worcestershire and allspice then cook 10 minutes, stirring frequently. Add wine and scrape up pan bits. Add stock and loosen up the mixture a little. Add tomatoes and parsley and heat through, 1 to 2 minutes. Fill breads and top with a thin layer of mozzarella and a sprinkle of Parmigiano or Romano. Broil the pizzas to melt cheese. Top each pizza liberally with basil and serve (with a fork and knife).