Fish en Papillote with Coconut Milk, Lemongrass, and Shiitakes

Fish en papillote is a French method of steaming fish in parchment paper, usually with herbs and aromatics, butter, vegetables, and a lemon wedge. For our version, we took inspiration from the Thai pantry, mixing together coconut milk, lemongrass, fish sauce, and lime juice, which we use to season both the fish and fresh shiitake mushrooms.