Clean, wash and cut the leek into rings. Heat the fat and stir-fry the leek for about 5 minutes. Stir in cheese. Season with salt and pepper and simmer for another 5 minutes.
Mix breadcrumbs and milk and let it swell. Peel onion and garlic and cut into fine cubes. Knead minced meat, ground pork, onion, garlic, egg, breadcrumbs and mustard. Season with salt and pepper.
Place 2 pieces of foil on the work surface (40 x 40 cm) and spread the chopped dough on top to form a square (approx. 30 x 30 cm). Spread 1/3 leek vegetables on the middle of the chopped dough. Roll up to a roll with the help of the foil and press the dough well together.
Turn in roasted onions and put them on the greased fat pan. Cook in the preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: level 2) for approx. 1 hour. Cover with aluminium foil if necessary.
Remove the roast and let it rest for a short time. Warm up the vegetables. Cut roast into slices. Arrange vegetables and roast. Garnish with parsley. Boiled potatoes taste good with it.