Finely slice the fennel stalks and bulb. Peel and finely slice the onion. Roughly chop the parsley. Cut one orange into slices, keeping the peel on. Place all the fennel, half of the onion, orange slices, and half of the parsley on the bottom of a roasting tray.

Preheat the oven to 240°C (475°F).

Drizzle olive oil inside the cavity of the fish. Stuff the cavity with the remaining parsley, orange juice, and season with black pepper and salt. Close the cavity with a toothpick. While I don't have video, the attached images show the process.

Place the prepared sea bass on the baking tray with the fennel, onion, and parsley. Pour over vermouth, 2 tablespoons of olive oil, and add the butter. Squeeze the juice from one orange over the fish. Place the tray in the preheated oven and immediately reduce the temperature to 180°C (350°F). Roast the fish for 30 minutes or until fully cooked.

Scrunch the remaining sliced onion in a little vinegar to quickly pickle it. Serve with olives and the roasted vegetables from the tray. Drizzle the fish with a little extra olive oil before serving.