Cook the spinach in a heavy casserole pan with a little bit of salt
Clean the squid by removing the head and innards from the outer part (main body)
Cut the head just after the eyes and remove the cartilage
Clean well in cold water to remove any sand or bad bits
Chop the head and tentacles finely
In another pan, cook with chopped onion, in a bit of oil, add salt and pepper as necessary
Add garlic, parsley and cooked spinach
Cook for a few minutes
Add the breadcrumbs and mix well
Remove from the heat and allow to cool slightly
Add egg, salt and pepper, mix well
Stuff the squid body with the spinach mixture, until slightly over ¾ full. Do not overfill.
Close the tops with toothpicks
In a heavy saucepan on medium heat, fry the squid in a bit of oil until it starts to turn slightly pink
Remove the squid and set aside
Add tomato concentrate, wine, water, bay leaves, fennel stick and Piment Espelette to the pot. Mix well.
Place the squid in the sauce, cover and cook on medium heat for about 45 minutes