Halibut Steaks with Mussels

One of France’s great seafood classics is sole à la normande. Hardly anybody makes it anymore because it requires a sauce normande, a hopelessly elaborate concoction of fish broth, mussel cooking liquid, mushroom cooking liquid, fish velouté, and loads of butter, egg yolks, and cream. A garniture of shrimp, mussels, oysters, truffles, and puff pastry is then arranged on top of the whole cooked sole. But like so many classic dishes, sole à la normande can be simplified and lightened for mode