1. Scrub the mussels well with a brush under cold running water, discarding any with cracked shells or shells that fail to close when tapped. Using needle-nose pliers, pull out and discard any clumps of black strings at the hinges of the mussels. Using a metal skewer or an old pointy knife, poke holes in the bottom of one of the aluminum foil pans. Pierce the foil with the skewer or knife tip, then twist it to make a 1/2-inch hole. The holes should be spaced 2 inches apart.

2. Fill the perforated foil pan with the pine needles; they should be loosely mounded rather than tightly packed. Arrange the mussels on top.

3. Set up the grill for direct grilling and preheat it to high. In the best of all worlds, you’ll be grilling over a wood fire. Charcoal is the second-best choice, but you can also do this on a gas grill. There is no need to oil the grill grate.

4. When ready to cook, place the pan with the mussels on the hot grate. The pine needles will start to smoke and catch fire after a few minutes. If you’re working on a gas grill, you may need to use a butane match or lighter to help ignite the pine needles. Once the pine needles have caught fire, place the second foil pan over the mussels and pine needles. Grill the mussels until the shells open and the bivalves are cooked, 5 to 8 minutes.

5. Once the mussel shells begin to open, sprinkle the mussels with the raspberry vinegar, if using. Cover the mussels again and grill for 1 minute longer. The vinegar is optional, but it adds an extra dimension of flavor.

6. Transfer the smoking, steaming pan with the mussels to a heatproof platter and serve the mussels at once, discarding any that have not opened. You eat the mussels with your fingers right out of the pan. Melted butter can be served on the side, but you really don’t need it.