Cook Maultaschen in boiling broth for 10-12 minutes. Peel onions and cut into rings. Clean, wash and drain lamb's lettuce well
Take out the Maultaschen and let them drip off. Mix vinegar and mustard. Season with salt, pepper and sugar. Fold in the oil. Cut Maultaschen into strips. Mix with salad, onions and vinaigrette. Season salad and serve immediately