6. To give the sauce the smooth texture Ben blends it in a food processor to ensure all the herbs are fully incorporated, he then salts it “as salty as the sea” (because the potatoes are not seasoned and like sponges) and adds some pepper and a zest of lemon.
Crucially Ben then leaves the sauce to cool so it doesn’t cook the potatoes when mixed in with them.
7. To get the potatoes fully coated in the sauce Ben uses a huge bowl – the biggest you can find to literally “bathe” the potatoes in the sauce, and separate each individual slice.
8. Once fully coated, ‘shuffle’ the potatoes together like cards and stand them up in the dish – Hasselback style. They should be packed in as tightly as possible with any gaps filled in.
source: express.co.uk