Heat a tablespoon of oil in a pan over medium heat. Sauté the chopped mushrooms and half of the onion until the moisture evaporates and they are golden brown. Season with salt and pepper, then set aside to cool completely.

Soak the stale bread in the milk for 5 minutes until soft. Squeeze out the excess milk.

In a large bowl, combine the ground pork, the soaked bread, the remaining raw onion, the egg, marjoram, 1 teaspoon of salt, and 1/2 teaspoon of pepper. Mix by hand until the mass is sticky and uniform.

Divide the meat mixture into 4 equal portions. Flatten one portion in your hand to create a disc.

Place a spoonful of the cooled mushroom mixture into the center of the meat disc. Carefully fold the edges of the meat over the filling and seal it, shaping it into an oval patty.

Pour the breadcrumbs onto a flat plate. Roll each patty in the breadcrumbs, pressing gently to ensure an even coating.

Heat oil in a large skillet over medium heat (about 1/4 inch deep). Fry the patties for roughly 5-6 minutes per side until they are deep golden brown and cooked through.

Drain on paper towels and serve hot with mashed potatoes and beet salad.