Wash the meat, dab dry and season all around with salt and pepper. Place meat lying on the bone in the fat pan of the oven and roast in the preheated oven (electric: 200 °C/ gas: level 3) for approx. 1 1/4 hours. In the meantime, clean, wash and peel the carrots. Leave some of the greenery to stand. Cut off the lower hard ends of the asparagus.
Clean the mangetout. Wash the asparagus and sugar snap peas. Cook the carrots in salted water for about 12 minutes. Cook the asparagus in boiling salted water for about 15 minutes. 5 minutes before the end of the cooking time, add the mangetout and cook. Drain the vegetables, collecting the cooking water from the carrots and measuring 300 ml. Melt the fat in a saucepan. Dust with flour and sauté. Deglaze with cooking water and cream while stirring and bring to the boil. Season to taste with salt and pepper. Remove sauce from the heat, add egg yolk and fold in.
Dust with flour and sauté. Deglaze with cooking water and cream while stirring and bring to the boil. Season to taste with salt and pepper. Remove sauce from the heat, add egg yolk and fold in. Arrange roast, vegetables and some sauce on a plate and serve sprinkled with chervil and pepper. Add the rest of the sauce extra. Serve with croquettes