Rinse the lentils, place in boiling water and cook for 35-40 minutes. Clean, wash and slice the mushrooms. Clean, wash and drain the salad. Peel and finely chop the onion.
Mix vinegar, sugar, salt and pepper. Fold in the oil. Mix lentils and marinade and let it soak through a little. Rinse sprouts briefly. Cut cheese into cubes. Peel beetroot and slice finely.
Mix lentils, mushrooms and cheese. Serve with beetroot, lamb's lettuce and sprouts on plates. Serve with baguette bread.