Heat the sunflower oil in a large saucepan to 180°C, the oil should be 1/3 of the way up the sides.
Dry the squid, slice and open out the tubes like a book.
Lightly score the inside of the squid by cutting a crisscross pattern onto the surface then cut into wide strips. Add the squid to the buttermilk and toss well to coat so they’re submerged.
Bash the fennel seeds in a pestle and mortar and add to a wide dish with the cajun and plain flour, along with lots of salt and pepper.
Remove the squid from the buttermilk and place in the bowl with the flour. Coat each piece of squid making sure to press them into the cajun flour mix, arranging on a tray as you go. They should be evenly and well coated. Once coated, work in batches and cook the squid in the oil for 1 to 2 minutes until golden and crispy.
Drain on kitchen paper to absorb any excess oil.
To serve, blend the mayo, basil leaves and garlic together until smooth and pop in a dish for dipping and dunking.