The crescia con salsiccia e spinaci is the cooked-filling version of the Urbino flatbread: the same flaky, peppery crescia off the testo stone, split warm and packed with crumbled sausage and wilted spinach. Where the prosciutto version stays cold and spare, this one is a hot filling, and that changes the whole reading. The sausage is loose Italian salsiccia, the meat broken from its casing and cooked down so it goes craggy and rendered rather than sliced, and the spinach is wilted in the same pan so it carries the fat. The defining fact is that the crescia here is a container for something warm and a little wet, not a frame for something cured and dry.
The craft is moisture control against a bread that resists it. The crescia is laminated with lard and built to stay flaky, so a wet filling would collapse its sheets if it went in dripping. The spinach is wilted hard and squeezed so it gives up its water before it meets the bread, and the sausage is drained of its loosest fat so the crumb firms against the filling instead of going to mush. The bread is split while still warm so its leaves stay crisp at the edges and the heat of the filling does not have to fight a cold shell. The pepper worked into the crescia is the only seasoning the spinach needs; the sausage brings its own salt and fennel.
This is one filling on a bread that takes many, and the others stand on their own. The same layered round laid cold with prosciutto crudo and rocket is the Crescia con Prosciutto e Rucola; the bread itself, treated as the achievement it is, is the Crescia Sfogliata. Each is this Urbino flatbread met by a different filling, and each deserves its own article rather than being crowded in here.