Step 1

Stir together 2 tablespoons salt, pepper, juniper berries, and garlic in a small bowl. Place chicken in a large bowl; sprinkle with spice mixture. Add thyme and rosemary sprigs; toss well. Cover and chill 4 hours.

Step 2

Place potatoes in a large saucepan; add 2 quarts water and remaining 2 tablespoons salt. Bring to a boil over medium-high. Reduce heat to medium-low; simmer until potatoes are fork-tender, 20 to 25 minutes. Drain and let cool to room temperature.

Step 3

Place shallot in a medium bowl; sprinkle with salt. Add lemon juice and vinegar. Let stand 5 minutes. Whisk in mustard. Add olive oil, 1 drop at a time, whisking vigorously, until fully emulsified, and then begin pouring in a slow, thin stream, whisking constantly, until oil is fully incorporated and dressing is creamy. Finely chop chives to equal 2 tablespoons; reserve remaining chives. Stir chopped chives and pepper into dressing. Season to taste with salt. Cover and refrigerate until ready to serve.

Step 4

Let chicken stand at room temperature while preheating grill. Open bottom vent of a charcoal grill completely. Light charcoal chimney starter filled with briquettes. When briquettes are covered with gray ash, pour onto bottom grate of grill, and push to one side of grill. Place hardwood chunks on top of hot coals. Coat top grate with canola oil; place on grill. Discard herb sprigs from chicken. Place chicken quarters, skin side down, on oiled grates over side with coals. Grill, uncovered, until skin begins to crisp, rotating chicken pieces as needed over hottest part of grill, 2 to 4 minutes. As skin crisps, flip chicken skin side up, and move to side without coals, positioning bones toward coals. Once all pieces are arranged over side without coals, cover grill with lid positioned so that top vent is above chicken; adjust vents as needed to maintain an internal grill temperature of 375°F to 400°F. Roast chicken, rotating pieces as needed for even cooking, until a thermometer inserted in thickest portion of breasts and thighs registers 155°F, 45 minutes to 1 hour.

Step 5

Meanwhile, place cooked potatoes on a cutting board or a flat work surface. Using the bottom of a measuring cup, gently smash potatoes, 1 at a time, to about 1/2-inch thickness. Arrange potatoes on a large platter. Season with salt to taste. Place lettuce and radishes in a serving bowl. Chop remaining chives into 2-inch pieces, and scatter over salad.

Step 6

Remove chicken from grill, and place on top of potatoes; cover with foil, and let rest 10 minutes. Transfer chicken to a cutting board; separate legs from thighs, and slice breasts into 1-inch pieces. Return chicken to platter with potatoes, and drizzle with 1/2 cup shallot dressing. Drizzle salad with 1/4 cup dressing. Serve remaining dressing on the side.