In a large pot, combine water, halved onion, smashed garlic cloves, black peppercorns, kosher salt, lemon juice, parsley stems, and bay leaves. Bring to a boil, then add the baby octopus. Reduce heat to low and simmer for about 1 hour, checking for tenderness at 45 minutes.

Carefully drain the cooked baby octopus from the pot, discarding the aromatic ingredients. Allow it to cool before marinating.

In a separate bowl, whisk together extra virgin olive oil, minced garlic, lemon zest, and red chilli flakes. Pour the marinade over the warm octopus and cover with plastic wrap. Refrigerate for at least 12 hours, preferably 24.

Preheat your grill or stovetop skillet over medium-high heat. Brush with canola oil, then add the marinated baby octopus. Grill for about 3-5 minutes, rotating halfway through until nicely charred.

Transfer the grilled octopus to a serving platter. Garnish with chopped parsley and sliced red chili. Serve with lemon wedges.