30 baby potatoes (1 to 1 1/2 inches in diameter; 1 3/4 lb total)
1 tablespoon plus 1 teaspoon coarse kosher salt
3 tablespoons extra-virgin olive oil
Special equipment: 12 (6- to 8-inch) woody rosemary stems or bamboo skewers, soaked in water 30 minutes
Cover potatoes by 1 inch in cold water in a 4-quart pot, then add 1 tablespoon kosher salt and bring to a boil over high heat. Reduce heat and simmer until potatoes are just tender, 12 to 15 minutes.
Drain potatoes in a colander and transfer to a large shallow pan to cool quickly.
If using a charcoal grill, open vents on bottom of grill, then light charcoal. Charcoal fire is hot when you can hold your hand 5 inches above rack for 1 to 2 seconds. If using a gas grill, preheat burners on high, covered, 10 minutes, then reduce heat to moderately high.
Meanwhile, toss potatoes with 1 tablespoon oil and remaining teaspoon kosher salt, then push 2 or 3 potatoes onto each rosemary stem.
Grill potato skewers directly over coals, turning over occasionally with tongs, until grill marks appear, 3 to 4 minutes total.
Transfer potatoes to a platter and drizzle with remaining 2 tablespoons oil.
