In medium glass bowl with lid, whisk together yogurt, garlic, gingerroot, 1 Tbsp (15 mL) avocado oil, lemon juice, garam masala, Kashmiri chili, coriander, cumin, cinnamon, sea salt, pepper, turmeric, fenugreek, and cardamom. Pat chicken thighs dry with paper towel and, with sharp knife, carefully cut diagonal slits deep into chicken thigh. Submerge chicken thighs in yogurt marinade. Cover marinating chicken and refrigerate overnight or up to 48 hours.
