3 pounds fingerling potatoes, sliced 1/4 inch thick
1 Spanish onion, thinly sliced
3 large garlic cloves, minced
1 fennel bulb, thinly sliced
1/2 lemon, thinly sliced and seeded
1/4 cup plus 2 tablespoons extra-virgin olive oil
1 tablespoon kosher salt
1 teaspoon freshly ground pepper
2 thyme sprigs
2 rosemary sprigs
2 bay leaves
Light a grill. In a large bowl, toss all of the ingredients. Tear off four 20-inch-long sheets of extra-heavy-duty aluminum foil. Arrange 2 sheets side by side and cover each with a second sheet. Mound half of the potatoes on half of each foil sheet, making sure that there's a thyme sprig, a rosemary sprig and a bay leaf in each mound. Fold the foil over the potatoes and crimp the edges tightly to seal.
Set the packages on the grill and cook over moderate heat, shaking them occasionally, until the potatoes are tender, about 40 minutes. Using tongs, carefully transfer the packages to a platter. Open and spoon the potatoes into a bowl.