Cover the meat with cold, lightly salted water, bring to the boil and simmer for 1.5 hours with the lid closed. Remove, let cool slightly, remove fat, cut into small cubes and set aside.
Cook the carrot, kohrabi and potato cubes in the meat broth for about 14 minutes, then add the frozen peas and beans and cook for another 12-14 minutes, add the meat again and heat.
Melt the butter in a saucepan, dust with the flour, sweat until lightly, deglaze with water, stirring constantly, and simmer for a few minutes. Stir these roux into the simmering stew and season with salt, pepper and sugar.