• Thaw the frozen octopus completely, then rinse quickly under cold running water. Set aside.
• Bring a large pot of water and 1 heaped tablespoon of salt to a boil.
• When the water is boiling, dip the octopus tentacles in the water 3 times, then fully submerge.
• Bring back to a boil, then lower the heat and simmer gently for 25-45 minutes or until tender when pierced in the thickest part with a fork.
• Once the octopus is cooked, remove the pot from the heat and let it cool in its cooking liquid. Turn it over from time to time.
• When cool, drain the octopus and cut into 1-inch (2.5 cm) pieces, cutting off and discarding any loose skin. Add the octopus pieces to the potatoes.
• In the meantime, cook the potatoes. Wash the potatoes well and place them in a large pot, cover with cold water, and add 1 heaped tablespoon of salt.
• Bring the water to a boil and cook for 15-20 minutes or until the potatoes are tender.
• Drain the potatoes and peel them. Cut the potatoes into 1-inch pieces and place them in a large bowl with the sliced red onion.
• Pour the dressing over the octopus and potatoes. Stir gently but thoroughly to combine. Taste and adjust seasonings as desired.

Make the dressing

• In a small bowl, whisk together olive oil, chopped parsley, lemon juice, minced garlic, salt, and pepper. Set aside until needed.