How to Make It
Combine wine, onions, rosemary, bay leaves, 2 tablespoons of the salt, and 4½ quarts of the water in a large stockpot over high; bring to a boil. Using tongs, carefully dip octopus tentacles in boiling water 3 times, leaving octopus in water after third time. Reduce heat to medium-low, and cook until very tender, 2 to 2½ hours. Remove from heat, and let cool in liquid 2 hours.
Combine potatoes, ½ tablespoon of the salt, and remaining 8 cups water in a saucepan over high; bring to a boil. Reduce heat to medium, and simmer until just tender, about 10 minutes. Drain, and set aside.
Preheat a gas grill to high (450°F to 500°F). Heat 1 tablespoon of the oil in a large skillet placed on grill grate. Add chorizo to skillet, and cook until chorizo begins to crisp, 6 to 7 minutes. Add potatoes, thyme, and paprika. Cook, stirring often, until potatoes begin to brown, 6 to 7 minutes. Remove from heat.
Toss octopus in 3 tablespoons of the oil. Place on grill grate. Cook until deeply charred, 3 to 4 minutes per side. Combine potato mixture, grilled octopus, vinegar, and remaining 3 tablespoons oil in a large bowl; sprinkle with half of parsley and remaining 1 teaspoon salt, and toss to coat. Place mixture on a large platter. Sprinkle with Espelette and remaining parsley.