Preheat oven to 400°F (205°C). In a small bowl, mash the softened grass-fed butter with minced garlic, chopped rosemary, thyme, parsley, lemon zest, and a pinch of salt until thoroughly combined.

Thoroughly pat chicken breasts completely bone-dry with paper towels—dry skin is essential for shattering crispness. Gently separate the skin from the meat using your fingertips. Spread 1 tablespoon of the herb compound butter directly under the skin of each breast, massaging it evenly across the meat.

Rub the chicken skin with olive oil, salt, black pepper, smoked paprika, and onion powder. Heat a heavy oven-safe cast iron skillet over medium-high heat. Sear chicken skin-side down for 3 to 4 minutes until deeply browned and blistered. Flip skin-side up.

Scatter the halved garlic head and fresh herb sprigs into the skillet. Pour chicken bone broth around the chicken (not over the crispy skin). Dot the remaining herb butter over the breasts. Transfer the skillet into the oven and roast for 20 to 22 minutes, basting once with pan drippings halfway through.

Roast until an instant-read thermometer reads 160°F (71°C) in the thickest part. Transfer chicken to a cutting board and let rest for 8 minutes (carryover heat brings it to the USDA-safe 165°F while juices redistribute). Swirl a splash of lemon juice into the hot skillet drippings to create a rich pan sauce. Carve into thick succulent slices, spoon pan jus over top, and serve immediately.