In a small bowl, combine 1/4 cup of the breadcrumbs with the whole milk and let the mixture sit for 5 minutes until the breadcrumbs absorb all the liquid and soften.

In a large mixing bowl, combine the ground pork, ground beef, minced onion, egg, soaked breadcrumbs, salt, and black pepper. Knead the mixture thoroughly with your hands for about 5 minutes until it becomes smooth, sticky, and completely uniform.

Divide the meat mixture into 8 equal portions, shape each into a thick oval patty, and flatten them slightly. Roll each patty in the remaining 1/4 cup of dry breadcrumbs until they are evenly coated on all sides.

Heat the vegetable oil and butter in a large skillet over medium heat until the fat is hot and shimmering. Place the patties in the skillet, leaving space between each, and fry for 8 to 10 minutes on the first side until deeply golden brown and crispy.

Carefully flip the patties and fry the other side for another 8 to 10 minutes until fully cooked through and the internal temperature reaches 160°F (71°C). Serve these warm patties immediately alongside mashed potatoes and a fresh cucumber dill salad.