You'll need to begin this recipe at least a week ahead to make
1½ tspfennel seedsFinelygrated rind and juice of ½ lemon500 gmkipfler or chat potatoes, scrubbed, halved½small Spanish onion, thinly sliced1 tbspred wine vinegar1 tbspcrème fraîche1 tspDijon mustard65 mlolive oil150 gmbaby cucumbers, half-peeled, halved lengthways, coarsely chopped150 gmhot-smoked trout, coarsely flaked1fennel bulb, thinly shaved on a mandolin, placed in acidulated waterPickled baby cucumbers250 gmbaby cucumbers, unpeeled, halved lengthways125 ml (½ cup)white wine vinegarJuiceand thinly peeled rind of 1 lemon1 tsp eachfennel seeds and coriander seeds½ tspdried chilli flakes
For pickled baby cucumbers, layer cucumbers snugly in a sterilised jar and set aside. Place remaining ingredients, 2 tsp sea salt and 200ml water in a saucepan over medium-high heat, stir until sugar dissolves and bring to the boil. Pour over cucumbers, seal and stand to pickle (at least a week). Pickled baby cucumbers will keep refrigerated for 2 months.
Dry-roast fennel seeds until fragrant (30 seconds), pound in a mortar and pestle with lemon rind and 1 tsp sea salt and set aside.
Combine potato in a saucepan with a generous amount of cold, salted water, bring to the boil over medium-high heat and cook until just tender (10-12 minutes). Drain, transfer to a large bowl and cool to room temperature.
Combine onion, lemon juice and vinegar in a bowl, stand until onion has softened (2-3 minutes), then transfer onion with a slotted spoon to potato. Whisk crème fraîche and mustard into vinegar mixture, whisk in oil and fennel seed mixture, then add to potato mixture. Add cucumber, trout and drained fennel and toss lightly to combine. Drain half the pickled baby cucumbers, coarsely chop, add to salad, toss to combine and serve with remaining pickled baby cucumbers to the side.