Prepare the pasta in boiling salted water according to the instructions on the packet, then drain. Cook lentils in boiling water for about 12 minutes, also drain. Mix the noodles and lentils. Peel and halve the onions and cut into strips. Heat vinegar, add onion strips. Season with salt, pepper and sugar, remove from the heat.
Stir mustard into it, add oil. Pour over the noodles while still warm, cover and leave to stand for about 30 minutes. In the meantime wash, clean and drain the lamb's lettuce. Slice the parmesan. Mix ingredients and pasta mixture. Season to taste again and serve