The schiacciata con mortadella is the meeting of a warm oiled Tuscan flatbread and a soft pink cooked sausage that the bread is built to slacken. Schiacciata, the squashed one, is a low leavened dough pressed flat, dimpled, rubbed with olive oil and salt, and baked until the top is gold and lightly crisp over a soft, open crumb. Mortadella is the wide Bolognese cooked pork sausage, finely emulsified, dotted with cubes of white fat and often pistachio, sliced into floppy sheets that drape rather than stack. The defining fact is the partnership of warmth and softness: the schiacciata's oil-touched crumb, still holding oven heat, eases the mortadella's fat from firm to silky, while the sausage gives the otherwise plain flatbread its full richness and its faint, sweet, lightly spiced perfume. Without the mortadella the schiacciata is bare oiled bread; without the soft flatbread the sausage has no warm surface to melt against. The two are matched so a quiet bread turns a gentle sausage into a full bite.
The craft is in heat, the slice, and the fold. The schiacciata is best used warm and split horizontally so the inner faces meet the meat, because the residual warmth is what loosens the mortadella's fat and binds the two without any added sauce. The mortadella is sliced thin and ribboned loosely into the bread, folded into soft waves so it traps a little air and the bite stays light, never packed flat into a dense slab that would weigh the flatbread down and squeeze the fat out. Nothing wet is added, since the sausage already carries salt, fat, and its mild spice, and the bread's own oil is the only fat the build needs. A sloppy version uses a cold dense flatbread and a thick stacked wad that reads as one greasy note; a good one is warm and soft, loosely but generously filled, and balanced so the plain bread and the cushiony sausage add up.
The close cousins stay in the Tuscan oiled-flatbread habit, each its own subject rather than a footnote here. There is the schiacciata con finocchiona with fennel salame, the schiacciata con salame toscano with the plain pepper salame, the schiacciata con lardo di Colonnata built on cured back fat, and the relative on a rosetta with the same mortadella in a hollow roll instead of a flatbread. Each is the same oiled-flatbread-meets-cured-pork idea with one element changed, and each deserves its own article rather than being crowded in here.