I love using the heat of the grill to open shellfish. I think they come out as juicy as if they were roasted in the oven. The flavors of garlic, parsley and mint make this a great opener to a meal or a nice side dish or nibble. The crunch of the bread crumbs is also a great texture contrast to the mussels and the flavors evoke the natural sweetness of the mussels.
Preheat the grill or grill pan to medium.
Heat a large skillet over low heat and add the olive oil. When the oil is warm add the garlic. Stir the garlic with a wooden spoon and season with salt, to taste. Give the garlic a minute to "melt" into the oil but do not let it brown. Stir in the bread crumbs, parsley and mint. Taste for seasoning, Set aside.
When the grill is hot, scatter the mussels on the grill in a single layer. Have a pair of tongs and a large platter ready. As the mussels open, use the tongs to remove them from the grill onto a platter. When they are all opened, squeeze the juice from the lemons over them and spoon the bread crumb mixture into the shells. Serve immediately.