Spicy Herby Calamari Rings

Put the calamari into a glass dish, pour over the buttermilk, then cover and place in the fridge for 30 minutes - 1 hour.
When you are ready to cook, pour the cornflour onto a plate, then season well with salt and pepper and set aside. Heat at least 5cm oil in a wide, heavy-based saucepan until it reaches 180°C / 350°F, or until the handle of a wooden spoon dipped into the oil forms lots of small, fizzy bubbles.
Meanwhile remove the calamari from the fridge, then dredge around half of the rings through the cornflour mixture, shaking off any excess. Fry the floured calamari in the hot oil for 2 minutes in total, removing with a slotted spoon when cooked and transferring to a warm plate lined with a paper towel. Flour and fry the remaining calamari.
Toss the hot calamari together with the chillies, spring onions, peanuts, parsley and rocket in a large bowl, then shake them out onto a large serving platter or individual plates. Serve with some lime quarters, more rocket if you like and Sweet Chilli Mayo.
To make the Sweet Chilli Mayo, whisk the egg yolk and lemon juice together until foamy. While beating, drizzle in the oil, whisking well until you have a thick emulsion. Stir through the sweet chilli and season to taste with salt, pepper and extra lemon juice if necessary.