Peel the shallot and cut into fine cubes. Knead minced meat, shallot, mustard, egg yolk, breadcrumbs and 1 tablespoon of milk. Season with salt and pepper. Shape into 1 meatball. Prepare rice in boiling salted water according to package instructions.
Heat the oil in a pan and fry the meatball for 10-15 minutes, turning it over. Peel and wash the carrots and cut them lengthwise into quarters. Peel kohlrabi and cut into slices. Cook the prepared vegetables in boiling salted water for about 6 minutes.
Melt the fat in a pot. Stir in flour and sweat briefly. Add stock and 100 ml milk while stirring. Bring to the boil, boil for 3-5 minutes and season with salt and pepper. Wash the chervil, shake dry, pluck off the leaves, except for something to garnish.
Pour the vegetables into a sieve, add to the sauce and fold in. Arrange rice, vegetables and meatball on a plate. Sprinkle with chervil and garnish.