Wash the potatoes and cook in boiling water for about 20 minutes. Peel carrots, cut them in half lengthwise and cut them into thin slices at an angle. Wash and clean the beans. Cook the beans in boiling salted water for about 8 minutes.
Add the carrots approx. 2 minutes before the end of the cooking time. Drain beans and carrots, rinse briefly under cold water and allow to drain. Drain potatoes, rinse briefly under cold water, peel and possibly halve depending on size.
Heat 2 tablespoons of oil in a large frying pan. Fry the potatoes over medium heat for 8-10 minutes while turning. Add the beans and carrots 3-4 minutes before the end of the frying time. Wash parsley, shake dry and chop the leaves coarsely.
Wash the meat, dab dry and cut into cubes. Heat 2 tablespoons of oil in another pan. Fry the meat for about 6 minutes, turning it over, remove it and add it to the vegetables. Deglaze the roast with cream.
Add mustard and simmer for 2-3 minutes. Season the sauce with pepper and possibly a little salt.
Add butter to the vegetable-meat pan, let it melt, mix and season with salt and pepper. Pour mustard sauce over it and sprinkle with parsley. Serve immediately.