Onions peel and in fine cubes cut. Finely chop bread in the universal chopper and mix with 120 ml milk. Knead minced meat, ground pork, eggs, 2/3 of the onions, bread and mustard.
Season with 1 teaspoon salt and pepper. Form into an oval roast and cook in the greased fat pan of the oven in the preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: level 2) for approx. 1 1/2 hours.
Defrost peas at room temperature. Peel, wash and halve potatoes and cook in boiling salted water for about 20 minutes. Clean and clean the mushrooms and, depending on size, halve or quarter them. Heat 1 tablespoon of fat.
Add the remaining onion and sauté for about 6 minutes. After 2 minutes add mushrooms, dust with flour and deglaze with cream and 250 ml milk, bring to the boil and simmer for 3 minutes. Season to taste with salt.
Peel, wash and slice the carrots. Heat 1 tablespoon of fat, sauté carrots briefly, season with sugar and salt. Add 200 ml water, bring to the boil and stew the carrots for about 10 minutes. Add peas after 5 minutes.
Wash parsley, shake dry, pluck leaves from the stalks and chop. Take the finished roast out of the oven and cut into slices. Arrange roast, vegetables and sauce on a plate. Add potatoes sprinkled with parsley.