Preheat the grill to high. Make the sauce: pour the stock, cream and Noilly. Put into a medium-sized saucepan and boil rapidly until reduced by three-quarters. Turn off heat and keep warm.
Brush the salmon on all sides with half the melted butter and season. Place on a lightly buttered baking tray and grill for 8 minutes until just cooked through.
While the salmon is cooking, bring a large pan of salted water to the boil, add the kale and cook for 3-4 minutes. Remove, drain well and return to the pan, then add the remaining melted butter and toss. Cover pan to keep warm.
Bring the sauce to a simmer, then whisk in the chilled butter one piece at a time. Stir in the thyme and season to taste.
To serve, divide the kale between 4 warmed plates and top each with a piece of salmon. Spoon some of the sauce over the fish and the rest around the kale. Serve with steamed new potatoes and any remaining sauce in a small jug.