1.To make dill dressing: combine all the ingredients in a screw-top jar; shake well.
2.Steam potatoes until almost tender. Add peas, snow peas and sugar snap peas to boiling water; cook 1 minute; drain. Refresh peas in cold water; drain well. Cut snow peas and sugar snap peas in half lengthways.
3.Slice hot potatoes thickly and toss with 1/3 cup (80ml) of the dill dressing.
4.Heat about 2 cups (500ml) water with lemon and peppercorns in medium frying pan. When water is warm, add salmon; bring to a simmer. Simmer, covered, until salmon changes colour and is rare to medium in the centre. Drain; cool slightly, then flake into chunks.
5.Arrange potato, peas, salmon, spinach and mint on serving plates or platter.
6.Drizzle with remaining dill dressing.