Preparation

Season the birds

• In a small bowl, combine the garlic, tarragon, parsley, salt, and pepper.
• Rub the poussin all over with the oil, then with the seasoning, using most of it on the meatier side of the birds.

Make the glaze

• In a small saucepan, whisk the apple juice, wine, and tapenade over high heat, and bring to a boil. Lower to a simmer and cook, whisking occasionally, until reduced to about 1/2 cup, 10 to 20 minutes. Set aside.

Make the butter

• In a small bowl, combine the shallot, balsamic glaze, Espelette pepper, and salt, and allow to
  sit for 5 minutes for the flavors to develop. Add the butter, and stir to combine. Set aside.

Grill and glaze the poussin

• Prepare a high (500°F to 600°F) gas or charcoal grill fire. Oil the grate.
• Grill the poussin, breast sides down, until the skin has nice grill marks; 4 to 6 minutes. Flip the birds over, brush with the glaze, and cook for an additional 1 to 2 minutes on that side.
• Finish grilling the birds over indirect heat: For a gas grill, simply turn off all but one of the burners and adjust the heat as necessary to maintain a temperature of 350°F.
• For a charcoal grill, briefly remove the birds from the grill, then remove the grill grate. Use long-handled tongs to bank the hot coals to one side. Put the grate in place. Place an oven thermometer on the grate over the cooler area, close the lid, and let the coals burn down until the thermometer reads about 350°F.
• Transfer the birds to the cooler side of the grill and continue cooking, breast side up, brushing with the glaze every couple of minutes until cooked through (160°F), 25 to 30 minutes. (It’s fine if you run out of glaze before the birds are cooked.) You may want to rotate the position of the birds so the same ones are not always closest to the heat.

Butter, garnish, and serve

• Transfer the birds to a cutting board, breast side up, and spread with some of the butter. Tent with foil for 5 minutes. Cut into halves or quarters, garnish with the chopped tarragon and salt, and pass the remaining butter at the table.