1 Scrub potatoes and rinse, drain and cook in boiling, salted water for about 18 minutes or until tender. Drain and let cool a little and peel and set aside and let cool completely.
2 Rinse lettuce and spin dry. Chop walnuts coarsely and toast in a dry pan and set aside. Whisk egg yolks, vinegar and mustard until creamy and gradually add oil and season with salt and pepper.
3 Cut potatoes into 3 mm (approximately 1/8 inch) thick slices and heat butter in a pan and fry on both sides until crispy. Season with salt and paprika. Mix salad with part of dressing and place in a small bowl. Cut roast beef into bite-size pieces and mix beef and potatoes with remaining dressing. To serve, arrange roast beef and potatoes on salad and sprinkle with chopped walnuts.