Cook the cardinal lentils covered in 1 l boiling water for about 20 minutes. Finely dice onion, carrots and leek. Fry the leaves of 2-3 stalks of thyme in hot olive oil for about 10 minutes.
Sprinkle sugar over it, let it caramelize slightly and.
deglaze with balsamic vinegar. Bring to the boil and simmer for 2-3 minutes. Drain lentils well, add to vegetables and heat. Season to taste with salt and pepper.