Combine water, onion with skin, smashed garlic, black peppercorns, kosher salt, lemon juice, parsley stems, and bay leaves in a large pot. Bring to a boil over medium heat.

Add baby octopus and return to a boil. Reduce heat to low and simmer for about 1 hour until tender.

Remove octopus from pot and discard solids. Let cool for a few minutes.

In a mixing bowl, combine olive oil, remaining minced garlic, dried red chilli flakes, and additional lemon juice. Mix well.

Pour marinade over warm octopus, tossing gently to coat evenly. Allow to cool before covering and refrigerating for 12 to 24 hours.

Heat canola oil in a BBQ grill or skillet over medium-high heat. Sear marinated octopus for 3 to 5 minutes, turning to brown on all sides.

Transfer to a serving platter, garnish with parsley and red chili, and serve with lemon wedges.