Fegato alla Veneziana (Venetian Style Liver)

Rinse the calf's liver under cold water, pat it thoroughly dry with paper towels, then carefully remove any membranes or large veins. Slice the calf's liver thinly into strips, approximately 0.5 cm thick.

Peel and thinly slice the white onions into half-moons.

In a large, heavy-bottomed skillet, heat the extra-virgin olive oil and unsalted butter over medium-low heat.