Bring a pot of salted water to a boil and add the octopus, a couple of cloves of garlic, and white wine vinegar. Stir well and cover with a lid, lower the flame and cook slowly for about 1 hour, then turn off the heat and let the octopus cool off in the cooking water for about 30 minutes.
Add 2 potatoes to a pot of cold water and boil until just tender. Drain and dice into 1-inch cubes.
Remove the cooled octopus from the water and place it on a cutting board, slice the tentacles into 1-inch pieces and the head into small squares.
In a serving bowl mix together the octopus, potatoes, fresh parsley and remaining garlic. Season the octopus mixture with a generous drizzle extra-virgin olive oil, salt and pepper, to taste, and finish with some lemon juice.
Stir the salad well, cover it, and refrigerate for about 2 hours.
All you need is a glass of dry white wine and a slice of toasted bread!