For the vinaigrette: Place lemon juice, shallot, garlic and honey in a medium saucepan and reduce to 1/2 cup. Place reduced syrup into a blender, add olive oil and blend until smooth. Pour into a bowl and fold in the basil.
For the salad: Heat olive oil in a large saute pan over medium heat. Add the onions and cook until soft and caramelized. Add the vinegar and cook until reduced. Season with salt and pepper.
Place the octopus, water, vinegar, garlic, wine corks, bay leaf and peppercorns. In a medium saucepan and bring to a simmer over medium heat and cook until tender, about 3 hours. Remove the octopus from the water and place on a platter lined with paper towels. Heat the grill or grill pan. Cut the octopus into pieces, brush with olive oil, season with salt and pepper and grill for 1 to 2 minutes on each side.
Toss greens in a large bowl with 3 tablespoons lemon vinaigrette and season with salt and pepper. Place the greens on a large platter and top with the grilled octopus. Drizzle with more of the vinaigrette, top with the onion slices and sprinkle with the fresh herbs.