Frico is cheese, grated or cut into thin slices, cooked in a pan until a crisp surface forms. That shift from soft dairy to a brittle, golden sheet is the reason the dish rewards attention: heat does not merely melt; it builds a snap you can hear in the mind before the first bite.
One documented form relies on Montasio, and the more mature stages of that cheese are the ones suited to cooking. Age here is not a flourish. Firmer paste and concentrated flavour stand up to the pan, so the cheese can brown and set instead of collapsing into an oily puddle.
Recorded versions also allow onion, potato or apple as optional additions, never as a required trio. The useful distinction is simple: the pan-crisp cheese is the constant; those companions mark variation. When you next meet Frico, look first for that brittle surface, then notice whether sweetness, starch or allium has been invited in.