1.In a medium saucepan, place potatoes, covering with water and seasoning with salt. Boil for 15 minutes or until tender. Drain. Cut into 2cm slices.
2.Meanwhile, in a small bowl, whisk mustard, vinegar and dill; gradually whisk in oil. Season to taste.
3.In a large serving bowl, place warm potatoes with mustard dressing; toss gently to coat.
4.Discard skin and bones from trout; flake into large chunks. Add trout to potatoes with celery, shallot, salad leaves and capers; toss gently to combine.
Smoked salmon can be used instead of trout, if preferred.Note