Place the stale white bread slice in a small bowl, pour the milk over it, and let it soak for 5 minutes until completely soft.

In a large mixing bowl, combine the ground pork, finely grated yellow onion, egg, salt, and black pepper.

Squeeze the excess milk out of the soaked bread, tear it into tiny pieces, and add it to the seasoned meat mixture.

Mix the meat mixture thoroughly with your hands for 3 to 5 minutes until it becomes sticky, cohesive, and fully combined.

Divide the mixture into 4 equal portions and shape them into oval-shaped patties about 1 inch thick.

Place the dry breadcrumbs in a shallow dish, and roll each pork patty in the breadcrumbs until they are evenly coated.

Heat the unsalted butter and vegetable oil in a large skillet over medium heat until the fat is hot and shimmering.

Add the patties to the skillet and fry for 6 to 8 minutes per side, turning once, until they are deeply golden brown and cooked through to an internal temperature of 160°F.

Transfer the patties to a plate lined with paper towels to drain for 1 minute, then serve them hot with mashed potatoes and pickled cucumbers.