How to Make It
To prepare the octopus, use kitchen sheers or a sharp knife to separate the tentacles from the head by cutting just above the area where the legs come together (above the beak). At this point, you can divide the tentacles or leave whole.
Combine water, wine, peppercorns, salt, fennel, leek, garlic, bay leaves, and lemon in a large Dutch oven and bring to a boil. Add octopus to pan; simmer for 45-60 minutes (15-20 minutes per pound of octopus), until very tender when pierced with knife.
Turn off heat and, keeping the octopus submerged; let come to room temperature.
Remove octopus from the liquid. With a damp paper towel, wipe away skin and peel away the gelatinous, fatty layer from the meat. Chill meat until ready to use (the octopus can be prepped up to 3 days ahead).
To make the marinade, combine all ingredients in a medium glass bowl. Whisk well to combine. Thinly slice octopus (about ¼- to ½-inch pieces) and add to the mixture. Refrigerate octopus mixture for 30-45 minutes.
To prepare the salad, combine the first 6 ingredients (through mint) in a large bowl. Add marinated octopus and ¼ cup of marinade mixture to bowl; toss to combine.
To serve, spread labne onto a large serving plate and top with the tossed salad. Sprinkle with flaky sea salt and cracked black pepper to taste. Serve with crusty baguette or flatbread.