Cook the tongue in boiling water for 30-40 minutes. Peel kohlrabi and cook in boiling salted water for 20-35 minutes depending on size. Wash, clean and roughly chop the mushrooms. Peel and chop onion. Fry together in hot fat.
Dust with flour, pour on cream and stock and bring to the boil. Remove tongue from the cooking water, peel skin, remove fat and cartilage. Cut meat into cubes. Drain kohlrabi and chill in cold water. Hollow out with the help of a spoon, cut the inside into small pieces. Add the herbs, tongue and kohlrabi cubes to the mushrooms and heat briefly. Season with salt and pepper. Stir in egg yolk. Fill the kohlrabi with the ragout, sprinkle cheese over it. Bake in the preheated oven (electric: 200 °C/ gas: level 3) for about 10 minutes.
Add the herbs, tongue and kohlrabi cubes to the mushrooms and heat briefly. Season with salt and pepper. Stir in egg yolk. Fill the kohlrabi with the ragout, sprinkle cheese over it. Bake in the preheated oven (electric: 200 °C/ gas: level 3) for about 10 minutes. Arrange kohlrabi with the remaining ragout on plates. Garnish with herbs as desired