Pat the racks of lamb dry with paper towels to remove excess moisture.
In a small bowl, combine minced garlic, fresh rosemary, fresh thyme, dried rosemary, dried thyme, salt, and pepper to create a classic flavor blend.
Rub the mixture generously all over the racks of lamb, ensuring they are evenly coated. Let them rest in the refrigerator overnight, uncovered, on a sheet pan fitted with a wire rack for optimal flavor infusion.
When ready to cook, preheat your oven to 400ºF.
Heat a cast iron skillet (or heavy pan) over medium-high heat and add a splash of olive oil.
Once the pan is hot, sear the racks of lamb, fat side down, until golden brown, about 3-4 minutes.
Flip the racks and sear each side for an additional 1-2 minutes.
Add butter and fresh thyme sprigs to the pan. Baste the racks with the melted butter, spooning it over the lamb continuously for about 1-2 minutes.
Transfer the skillet to the preheated oven and roast until the lamb reaches your desired internal temperature (120ºF rare | 140ºF medium | 160ºF well-done).
Remove the racks from the skillet and let them rest on a cutting board for at least 10 minutes.
Carve the racks between the bones into individual chops, garnish with fresh herbs, and serve with your favorite sides.