In a mixing bowl, whisk together the grated garlic, lime juice, paprika, dried oregano, kosher salt, ground cumin, and ½ cup of olive oil to prepare the marinade.
Add the boneless, skinless chicken thighs to the marinade. Ensure each piece is well coated. Cover and refrigerate for at least 30 minutes, or up to 4 hours for deeper flavor.
Preheat your grill or grill pan over medium-high heat. Remove the chicken from the marinade and discard excess. Grill chicken about 6-7 minutes per side until internal temperature reaches 165°F. Let rest a few minutes.
In a blender or food processor, combine serrano pepper, cilantro, garlic, lime juice, honey, remaining 2 tablespoons olive oil, Greek yogurt, kosher salt, and 1 tablespoon water. Blend until smooth. Add more water if needed for desired consistency.
Slice the grilled chicken and serve warm, drizzled with the green sauce. Enjoy with rice, quinoa, or a fresh salad.