Cut the turbot into several pieces. Place the turbot pieces in a large ovenproof casserole or Dutch oven without overlapping them. Pour in the court bouillon. Bring to a boil. Reduce heat to a simmer, cover and cook for 15 minutes. Remove pan from heat and uncover. Leave to stand. Make the Hollandaise sauce: Place the egg yolks in the top of a double boiler with the vinegar and pepper and whisk to combine. Add the diced butter a little at a time, whisking constantly until the sauce has the consistency of mayonnaise. Stir in the lemon juice, a little at a time. Season with salt and pepper. Serve immediately or keep warm in a barely hot double broiler. To serve, drain the turbot and serve with the Hollandaise sauce and boiled potatoes.
