For the pickled beetroot:
- Scrub the beetroots in cold water then finely slice them 1.5mm thick, using a mandolin if you have one.
- Use a round pastry cutter to trim the beetroot slices, removing the skin, then put them in a heatproof container.
- In a saucepan, combine the vinegar, sugar and water and bring to the boil.
- Pour the liquid over the beetroot, making sure it is submerged, then cover and chill for 24 hours before using.
For the potato salad:
- Cut any large potatoes in half so they are all roughly the same size then simmer the potatoes in a large pan of salted water for about 20 minutes or until just tender.
- Use a hand blender to whizz the mustards, vinegar and treacle together in a jug.
- Slowly add the oil, blending continuously on low speed, until the dressing emulsifies. Be careful not to add the oil too quickly or the dressing will split.
- Season to taste with salt, pepper and a squeeze of lemon juice.
- When the potatoes are done, drain them and leave to steam dry for 5 minutes.
- Finely grate the zest from the lemon and finely chop the chives.
- Put the still-warm potatoes in a bowl, add the dressing, chives and lemon zest.
- Taste and adjust the seasoning then leave the salad to reach room temperature.
For the dill oil:
- Using a hand blender or small food processor, blend the dill and oil together until smooth.
- Strain through a fine-meshed sieve or muslin cloth and chill immediately until ready to serve.
- Divide the potato salad among serving plates and top with the smoked salmon.
- Choose the best looking slices of beetroot and arrange them on the salmon, around three per portion.
- Drizzle with the dill oil and garnish with avruga caviar and fresh dill sprigs.