Preheat the oven to 400 degrees F.
Season the Chilean sea bass fillets with salt and pepper. Dredge in flour, shaking off any excess.
In a large oven-proof skillet over medium heat, melt butter. Add shallots and garlic and cook until softened, about 2 minutes.
Add the Chilean sea bass fillets to the skillet and cook for 2-3 minutes per side, until lightly browned on each side.
Transfer the skillet to the oven and bake for 5-6 minutes until the fish is cooked.
While the fish is baking, prepare the sauce by stirring the white wine, chicken stock, lemon juice, orange juice, lemon zest, and orange zest. Bring to a simmer over medium heat and cook for 5 minutes or until sauce has thickened slightly.
Stir in the chopped thyme leaves and continue cooking for 2-3 minutes. Remove from heat and stir in the cold butter cubes until the sauce is smooth and creamy.
To serve, spoon the sauce over the cooked Chilean sea bass fillets.
Enjoy!