Chef Lentz plays off the mild flavor of trout with aromatic herbs and bitter greens that are bold but never overpower the fish. For cooking whole fish on the grill, the 10-minute-per-inch rule is a good guideline. Whole fish are actually a little easier to judge doneness than fillets, because they are already slit through to the center. Just peek inside the cavity and use the point of a knife to test the meat right next to the backbone. It should separate easily, and be just barely opaque. When the fish is done, let it rest 5 minutes before serving. Get more tips on how to cook trout.