Peel the onions, cut two of them into fine cubes. Clean, clean and chop the mushrooms. Cut bacon into fine cubes. Leave the bacon in a pan without fat until crispy.
Add onions and mushrooms and fry for about 6 minutes. Season with salt and pepper. Wash the meat and dab dry. Heat oil in a pan. Fry the meat on all sides over medium heat for 10-15 minutes.
Knead minced meat, liver sausage, 2 tablespoons mustard and mushroom mixture. Defrost puff pastry at room temperature. Place the pastry sheets on a floured worktop, slightly overlapping, to form a rectangle.
Spread a thin layer of cold water over the overlapping dough. Roll out dough sheets to a rectangle (approx. 35 x 35 cm). Spread the filling evenly on the dough, leaving a rim of approx. 4 cm free.
Coat the edges of the dough with water. Whip the meat into the dough. Press the edges of the dough well. Cut off excess dough and cut into strips with a dough wheel. Garnish the dough with it. Whisk the egg yolk and 3 tbsp. milk and brush the dough with it.
Place the casserole on a baking tray lined with baking paper and cook in a preheated oven (electric range: 200 °C/ convection oven: 175 °C/ gas: level 3) for approx. 45 minutes. In the meantime, clean and halve the savoy cabbage and remove the stalk.
Cut the savoy cabbage into small pieces. Dice the remaining onion. Heat butter in a pot. Fry diced onion until transparent. Add the savoy cabbage and stock and stew for about 15 minutes in a closed pot.
Season to taste with salt and pepper. Wash parsley, shake dry, pluck leaves from the stalks and chop. Mix sour cream, 2 tablespoons mustard, honey, 4 tablespoons milk and parsley. Season to taste with salt and pepper.
Cut smoked pork loin into slices and serve with butter savoy cabbage and sour dip.