Step 1

Place carrot, celery, onion, fennel, parsley stalks, wine, lemon zest and peppercorns in a large saucepan or stockpot and cover with 3L water. Simmer over medium heat for 25 minutes. Line a sieve with muslin or a clean Chux, then strain stock in a deep, wide pan, discarding solids.

Step 2

Return stock to medium-low heat and bring to a gentle simmer. Add the salmon and poach for 10 minutes. Remove from heat, cover and leave the salmon to cool completely in the liquid to finish cooking.

Step 3

Meanwhile, for the mayonnaise, place the egg yolks, mustard and lemon zest and juice in a food processor and whiz to combine. With the motor running, add oil in a slow steady stream until thickened.

Step 4

Add the chopped watercress and 2 tablespoons warm water, then whiz to combine. Season, then chill until needed.

Step 5

Place the potatoes in a large saucepan of cold, salted water. Bring to the boil over medium-high heat, then cook for 10 minutes or until tender. Drain, then toss with parsley leaves and butter. Allow to cool slightly.

Step 6

Using 2 spatulas, carefully remove the salmon from the poaching liquid. Break the salmon into large pieces and arrange on a serving platter with the potatoes and lightly dressed watercress sprigs. Drizzle with the watercress mayonnaise, season with sea salt and freshly ground black pepper and serve.