From Serious Eats, J. Kenji Lopez-Alt
2 pounds small yellow or red-skinned new potatoes
2 tablespoons minced fresh oregano, divided
2 tablespoons minced fresh parsley leaves, divided
4 medium cloves garlic, minced, divided
1/4 cup extra-virgin olive oil, divided
Freshly ground black pepper
1/4 cup thinly sliced scallions (about 4 whole scallions)
2 tablespoons minced shallots (about 1 small shallot)
1 tablespoon whole grain mustard
1 whole lemon
Place potatoes in a large pot and cover with cold water. Season generously with salt and bring to a boil over high heat. Simmer until potatoes are tender but not falling apart, about 5 minutes. Drain potatoes transfer to a rimmed baking sheet to allow excess moisture to evaporate.
When potatoes are cool enough to handle, split each one in half lengthwise and transfer to a large bowl. Add half of oregano, half of parsley, half of garlic, and half of olive oil. Season to taste with salt and pepper and toss roughly until potatoes are well-coated in the mixture and their surfaces are a little roughed up.
Combine remaining oregano, parsley, olive oil, garlic, scallions, shallots, and mustard in a large bowl to make a dressing.
Light your grill. When all the charcoal is lit and covered with gray ash, arrange the coals on one side of the charcoal grate. Set cooking grate in place, cover grill and allow to preheat for 5 minutes. Alternatively, set half the burners on a gas grill to the medium-high heat setting, cover, and preheat for 10 minutes.
Place potatoes cut-side-down over direct heat and cook, turning occasionally, until well-browned and crisp on both sides, 5 to 8 minutes total. Transfer potatoes to the bowl with the olive oil and herb mixture as they finish cooking.
Split lemon in half and place cut-side-down directly over heat. Grill until well browned, about 5 minutes. Squeeze grilled lemons into bowl with potatoes. Toss potatoes to thoroughly coat in fresh herb, olive oil, mustard, and lemon juice mixture. Season to taste with salt and pepper. Serve immediately.