Ingredients
1 (2 1/2 pound) octopus, head on, cleaned
3 cloves garlic
1 rib celery, cut crosswise into thirds, plus 1/2 cup very thinly sliced celery
1 carrot, peeled and cut crosswise into 3 even pieces
1/2 small white onion, coarsely chopped
1 bay leaf
3/4 cup dry white wine
1 pound mussels, scrubbed and debearded
2 pounds Manila clams
1 pound large (4- to 5-inch) squid, cut into rings with heads
2 cups thinly sliced radicchio
1 large red onion, very thinly sliced
1 cup fresh flat-leaf parsley leaves
1 cup extra-virgin olive oil
1 cup red-wine vinegar
Coarse salt and freshly ground pepper
Preparation
Place octopus in a large stockpot with garlic, 1 rib celery, carrot, white onion, bay leaf, and wine. Add 3 to 4 wine corks to pot to tenderize octopus. Place a lid smaller than the pot in the pot to keep octopus from floating and add enough water to cover by 3 to 4 inches. Bring to a boil over high heat; immediately reduce heat to a low simmer and cook, uncovered, until octopus is completely tender and easily pierced with the tip of a sharp knife, 1 to 1 1/2 hours, adding water as necessary to keep covered. Drain octopus, reserving cooking liquid, and set aside to cool.
Transfer 1/4 cup reserved octopus cooking liquid to a large heavy-bottomed stockpot. Add mussels and place over medium-high heat. Cover and cook until mussels open. Using a slotted spoon, transfer mussels to a large bowl and set aside.
Add clams to saucepan with cooking liquid; cover and cook over medium-high heat until clams have opened. Using a slotted spoon, transfer to bowl with mussels; set aside. Add squid to saucepan; cover and cook over medium-high heat until squid is translucent, 2 to 3 minutes. Transfer squid and cooking liquid to bowl with mussels and clams; set aside.
Slice tentacles of cooled octopus on the bias into 1-inch pieces and thinly slice body; add to bowl with mussels, clams, and squid. Add radicchio, thinly sliced celery, red onion, parsley, olive oil, and vinegar to bowl with seafood; season with salt and pepper and toss to combine. Let stand 2 hours; serve at room temperature.
