Place the bread slices in a small bowl and pour over the milk. Allow them to soak fully, then gently squeeze out excess liquid. This softened bread keeps the meatballs moist before moving on to mixing the meat.
In a large bowl, combine the minced meat, soaked bread, grated onion, garlic, egg, paprika, pepper, salt and marjoram. Mix gently using your hands until just combined, avoiding overworking the mixture. Cover and rest for 10 minutes to allow the flavours to settle.
With lightly damp hands, shape the mixture into oval or round patties about the size of a small palm. Aim for even thickness so they cook uniformly. Set aside while preparing the coating.
Lightly roll each fasírt in plain flour or fine breadcrumbs, shaking off any excess. This coating helps create the traditional crisp exterior once fried. Proceed directly to frying for best results.
Heat a generous layer of sunflower oil or lard in a wide frying pan over medium heat. The oil should be hot but not smoking. Test with a small piece of mixture to ensure gentle sizzling.
Place the meatballs into the pan without overcrowding. Fry for 4 to 5 minutes per side, turning carefully, until deeply golden and cooked through. Adjust the heat if browning too quickly.
Transfer the cooked fasírt to a plate lined with kitchen paper to remove excess oil. Allow them to rest briefly so the juices redistribute before serving.
Serve hot alongside mashed potatoes, parsley potatoes or a crisp cucumber salad. A spoonful of mustard or pickled vegetables on the side complements the richness beautifully.