In medium glass bowl with lid, whisk together yogurt, garlic, gingerroot, 1 Tbsp 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.
Next day, lightly grease broiling tray with 1 tsp avocado oil. Place tray on parchment-lined drip tray for easier cleanup. Remove chicken thighs from marinade and place on broiling tray. Broil chicken at 400 F for 22 minutes, flipping chicken halfway through and until internal temperature of chicken in thickest part is 165 F. Remove from oven and let rest for 5 minutes. Cut chicken into bite-sized pieces and cover with parchment paper until flatbread assembly.
While chicken cooks, prepare cilantro-lime crema. To small food processor, add yogurt, cilantro, garlic, cashew milk, lime juice, lime zest, onion powder, and sea salt. Blend ingredients until creamy, pour in glass bowl with lid, and set aside.
For flatbreads, in small bowl, whisk together tomato paste, olive oil, garlic powder, onion powder, Worcestershire sauce, and coconut sugar. Set aside.
Preheat oven to 425 F. On parchment-lined baking tray, place naan. Spread tomato sauce evenly among naans. Divide equally and top each naan, in order, with mozzarella cheese, diced tandoori chicken, red onion, green pepper, and mango. Bake in preheated oven for 8 to 10 minutes.
Remove flatbread from oven, top with cilantro-lime crema and chopped cilantro, and serve.