1/4 cup fresh lemon juice, plus lemon halves for grilling and serving alongside
2 tablespoons honey
1 tablespoon extra-virgin olive oil
2 medium cloves garlic, minced
Kosher salt and freshly ground black pepper
2 pounds boneless, skinless chicken breasts or thighs, cut into 1 1/2–inch chunks
If using bamboo skewers, soak skewers in water for at least 30 minutes. Meanwhile, in a large bowl, whisk together tarragon, mustard, lemon juice, honey, olive oil, and garlic. Season with salt and pepper. Toss the chicken in the marinade until fully coated, then cover and refrigerate for at least 1 and up to 4 hours.
Light one chimney full of charcoal. When all the charcoal is lit and covered with gray ash, pour out and spread the coals evenly over half of coal grate. Alternatively, set half the burners of a gas grill to high heat. Set cooking grate in place, cover grill, and allow to preheat for 5 minutes. Clean and oil the grilling grate.
Remove chicken from marinade and thread onto skewers. Discard the marinade.
Grill skewers over high heat until chicken has cooked through, about 3 minutes on each side (12 minutes total). If skewers threaten to burn, move them to the cooler side of the grill to finish cooking. Meanwhile, grill the lemon halves, cut side down, until lightly charred. Transfer chicken skewers to a platter and serve warm with the grilled lemons.