In a small saucepan over medium heat, combine the white wine, Grand Marnier, and grated ginger. Bring to a boil, and reduce the mixture by one half. Strain, and set aside to cool slightly. Whisk the reduction into the hollandaise sauce, and mix in orange juice concentrate. Preheat your oven's broiler. Place the filets onto a baking sheet, and dot each one with one teaspoon of butter, sprinkle with a pinch of thyme, and drizzle with 1/2 tablespoon of orange juice. Broil the fillets for 3 to 5 minutes, or until just barely done. Fish should be opaque and flake with a fork. Ladle sauce onto plates, and place yellowtail fillets onto sauce.