It's the 'poor man's salame', made with the cheap bits of pig and cow, but it's authentic, and prized in and around Genoa.(the good bits are made into a richer version called salame di Sant'Olcese. Generally sliced and fried, and served with polenta or bread or even fried eggs.
The village of Vicomorasso di Sant'Olcese throws a sagra della mostardella every April.
Images by: parodi