How to Make It
In a medium saucepan of boiling salted water, blanch the cabbage until barely tender, about 30 seconds. Plunge the cabbage into a bowl of ice water to stop the cooking. Drain and pat dry.
In a medium saucepan, boil the cider with the vanilla bean until reduced to 1/4 cup, about 10 minutes. Remove from the heat.
Preheat the oven to 400°. Scatter the bacon in a pie pan and roast for 15 minutes, or until crisp and most of the fat has been rendered. Transfer the bacon to a plate. Leave the oven on.
Meanwhile, in a small saucepan, combine the wine with the shallots, vinegar, peppercorns, tarragon stems and bay leaf. Boil until the liquid has reduced to 2 tablespoons, about 12 minutes. Strain the sauce into a small saucepan.
In a large ovenproof skillet, heat the vegetable oil until almost smoking. Season the salmon with salt and pepper and set the fillets in the skillet, skin side up. Cook over moderately high heat until browned on the bottom, about 2 minutes. Turn the fillets and cook for 2 minutes longer, then transfer the skillet to the oven and roast the fish until just cooked through, about 6 minutes.
Bring the wine reduction to a simmer and swirl in 4 tablespoons of the cold butter until smooth. Remove from the heat, add the tarragon leaves and chives and season with salt and pepper. Reheat the reduced cider over moderately high heat; discard the vanilla bean. Add the cabbage and bacon and cook until warmed through. Season with salt and pepper and swirl in the remaining 1/2 tablespoon of butter.
Spoon the cabbage onto 2 large warmed dinner plates. Set the salmon alongside, spoon the herb butter sauce on the fish and serve.