This salad has become a worldwide classic since being invented for a charity event at New York City's Waldorf-Astoria Hotel in 1896. For our modern, weeknight-friendly take on the cafe staple, honeyed nuts bring a sweet crunch and hot-smoked salmon makes for a fresh and fast change to traditional chicken.
Place walnuts in a small non-stick frypan over medium heat and cook for 2–3 minutes or until lightly roasted. Drizzle in honey and stir as the honey warms up. Keep stirring to completely coat nuts, then tip out onto a sheet of baking paper to cool completely.
Thinly slice celery stalks, apple and radishes into matchsticks. For nice, thin matchsticks, slice the apple and radishes into thin rounds first, then cut into matchsticks.
Carefully separate lettuce leaves and pick dill sprigs from their stems.
Combine mayonnaise and mustard in a bowl. Juice lemon. Add a few spoonfuls of lemon juice to dressing at a time and stir well to incorporate. Add as much or as little as you like, depending on your taste. Season with salt and pepper.
Flake salmon into large pieces and discard skin.
Toss celery, apple, radish, and lettuce in a bowl with dressing to thoroughly coat. Divide between bowls and scatter over salmon and dill sprigs. Break the cooled honeyed walnuts up using your fingers (you can chop them if they are stuck) and scatter over top to serve.