How to Make It
In a large, deep skillet, combine 2 quarts of water with the onion, garlic, parsley, prosciutto and salt. Cover, bring to a boil and simmer over moderate heat for 5 minutes. Add the octopus to the broth, cover partially and simmer over low heat until tender, about 1 hour; drain and pat dry.
In a small skillet, heat the vegetable oil. Add the black beans and cook over moderate heat for 2 minutes. Add the garlic, ginger and shallot and cook until softened, about 4 minutes. Add the red bell pepper and jalapeño and cook until starting to soften, about 2 minutes. Stir in the pear and remove from the heat. Stir in the lemon juice and chives.
In a small bowl, whisk the miso with the balsamic vinegar, oil, squid ink and 2 tablespoons of water. Season with salt and pepper.
In a bowl, mix the olive oil with the paprika and rub it all over the cooked octopus; season with salt. In a skillet, heat the vegetable oil until shimmering. Add the octopus and cook over high heat until browned all over, about 6 minutes. Transfer the octopus to a carving board and slice it crosswise 1/3 inch thick.
Spread the vinaigrette on 4 plates and top with the octopus. Spoon the black bean–pear sauce over the octopus. Garnish with the arugula and pear wedges and serve.