Wash the chillies, halve lengthways, deseed and chop. Peel and chop the garlic.
In a mortar, finely grind the garlic, chillies and some salt with half the coriander, cinnamon and cumin.
Drain the peppers and pat dry. Place the prepared spice mixture in a blender with the remaining coriander, cinnamon and cumin. Add the tomato paste, paprika and vinegar and blitz to a smooth paste.
Mix the homemade harissa with paprika and 2 tbsp oil.
Spoon the harissa paste into a small jar and cover with some olive oil. Seal and keep in the fridge for up to 3 months.
Pull out the squid tentacles from the body tubes, then cut off from the rest of the head so that they remain attached to a ring.
Remove the 'beak' from the base of the tentacles. Rinse and drain the tentacles.
Remove the transparent quil from the body of the squid and peel off the fine skin. Cut the fins from the sides.
Cut the tubes lengthways and remove the intestines. Thoroughly rinse the tubes under cold water and drain.
Place the squid on a board with the outer sides down and slash a diamond shaped pattern with a knife, not cutting all the way through.
Cut the body into pieces about 2cm wide and cut the tentacles in half.
Wash the coriander, shake dry and roughly chop the leaves.
Heat the remaining oil in a pan and fry the body and tentacles over a high heat for 1 minute on each side. Season with salt and pepper.
Add the harissa paste to the pan and mix with the seafood. Arrange the squid on plates with coriander and serve with bread, couscous or salad.