Cut the crusts off the bread and tear it into pieces. Soak in the 100 ml milk in a small bowl for 10 minutes, then squeeze out the excess milk with your hands.

Finely chop the cooked beef and mortadella by hand, or pulse in a food processor in short bursts until you get a coarse paste, not a smooth puree.

Combine the beef, mortadella, squeezed bread, eggs, parmesan, garlic, parsley, nutmeg, salt, and pepper in a large mixing bowl. Mix with your hands until everything holds together.

Cover the bowl and chill for 15 minutes. This firms up the mixture so the patties hold their shape in the pan.

Divide the mixture into 14 to 16 portions, about 40 g each. Shape each into a flat oval patty, roughly 1.5 cm thick.

Press each patty into the breadcrumbs, coating both sides evenly.

Heat the oil and butter in a 30 cm / 12-inch heavy-bottomed skillet over medium heat until it reaches 170 C / 340 F.

Fry the mondeghili in two batches so the pan isn't crowded, 3 to 4 minutes per side, until deep golden brown and the center reaches 74 C / 165 F on an instant-read thermometer.

Transfer to a wire rack to drain. Repeat with the second batch, adding a splash more oil if the pan looks dry.

Serve warm.