Refrigerate the marinated salmon for at least 2 hours, and no more than 4. Turn occasionally to mix things up.
For a charcoal grill, heap the coals to the side so you have a hot area and a warm area. Consider using real wood charcoal, as the briquettes impart a chemical taste to delicate meats. For a gas grill, set the temperature to medium-high heat: 375° F (190° C).
Use a grill brush to scrape off anything left over from previous cooking, if there’s anything.
Keep in mind that less is more with the cooking. You can always return it to the grill, but once it’s overcooked, there’s no way to salvage it.
Let the salmon rest for a couple of minutes after removing it from the grill to seal in the flavor and juices.
Lightly brush the grill grate with vegetable oil.
When the sauce has reduced down far enough so it’s starting to get thick (about 1 hour), strain the solids from the sauce with a sieve and return the liquid to the saucepan. Add the remaining port, and continue reducing until the sauce is thick and syrupy. If you still have a while until dinner, you can either remove the sauce from the heat, or add more port if you like. About 10 minutes before serving, add in the reserved blueberries.
Options. You can add other flavors to the reduction sauce, too. Some flavors that go well with this sauce include black peppercorns, rosemary, or chocolate. Experiment!
