Cook the potatoes in salted water until tender. Drain and season with maldon sea salt.
Place the butter in a pan over a medium heat and clarify. Skim off the foam that rises to the surface then remove from the heat. Pour the fat into a ug and discard the milk solids that collect at the bottom.
Squeeze the juice from the lemon.
Cut the vanilla pod in half and scrape the seeds into a heatproof bowl. Add the egg yolks, a tablespoon of water and whisk over a bain marie. Once doubled in volume, remove from the heat continue whisking whilst slowly adding the clarified butter. Once you have a thick sauce, add the lemon juice and season with salt and pepper. Set aside.
Season the salmon fillets with salt.
Heat a frying pan, add a little olive oil and sear the salmon (skin side first) for 3 minutes on each side.
Wash and season the rocket while the salmon is cooking.
Serve the salmon with the potatoes, a handful of rocket and a dollop of the vanilla hollandaise.
«Be careful not to overcook your salmon, 3 minutes on each side should be about right.»