In a very large pot, combine the water, halved onion (skin on), smashed garlic, peppercorns, 2 tsp salt, 3 tbsp lemon juice (or vinegar), parsley stems, and bay leaves. Bring to a rolling boil over high heat.

Drop the rinsed octopus into the boiling liquid. Bring back to a boil, then immediately lower to a gentle simmer.

Cook about 1 hour total, starting to check at 45 minutes; the tentacles should pull away easily and feel tender when pierced.

Pour the braised octopus into a colander. Discard the onion, bay leaves, and other aromatics. Transfer the warm octopus to a bowl while it’s still hot.

Whisk together 1/2 cup extra-virgin olive oil, 6 finely minced garlic cloves, 2 tsp lemon zest, 2 tbsp lemon juice, 1 tsp chilli flakes (if using), 1/2 tsp salt, and 1/2 tsp black pepper to make the marinade.

Pour the marinade over the warm octopus and toss thoroughly so each piece is coated. Let it cool to room temperature, then cover and refrigerate overnight.

Heat a BBQ hot plate or a large heavy skillet over medium-high to high heat, spreading a thin film of canola oil on the cooking surface to prevent sticking.

Using tongs, lay the marinated octopus on the hot surface, searing for 3-5 minutes and turning so each side gets blistered and crisp.

Serve right away, piling onto a platter and sprinkling with chopped parsley and sliced red chilli. Serve with lemon wedges and crusty bread for mopping the juices.