Preheat the oven to 425˚F.
Line a sheet pan with a piece of parchment paper.
Place the fish fillets on the parchment paper.
Sprinkle the fillets generously with kosher salt and freshly ground black pepper.
In a medium bowl, combine the crème fraîche, two mustards, and minced shallots. Gently fold in the capers. Add a 1/2 teaspoon of salt and sprinkle with more ground black pepper. Stir again to combine.
Evenly spoon the sauce over each fish fillet, making sure they are covered completely.
Bake the fish in the hot oven for 8 - 10 minutes, depending on the thickness of the fillets, until it's barely done. Do not overcook the fish. The fish should flake when a fork is placed in the fillet.
Serve the fish hot, spooning any extra sauce over the fillets, with your favorite roasted or baked vegetables,