In a large bowl, mix the yogurt, garam masala, coriander, turmeric, and red chili flakes.
Add the chicken pieces to the yogurt mixture, toss to coat well, and let marinate for at least 30 minutes in the refrigerator.
Heat the ghee in a large heavy-bottomed pan or Dutch oven over medium-high heat.
Add the sliced yellow onions and cook until deeply golden brown, about 10 to 15 minutes. Remove half of the onions and set aside for garnish.
To the remaining onions in the pan, add the minced garlic and grated ginger, sautéing for 1 minute until fragrant.
Add the marinated chicken to the pan and cook until it changes color and begins to brown, about 5 to 7 minutes.
Stir in the blended cashew paste and reduce the heat to low. Cover and simmer for 15 to 20 minutes, or until the chicken is fully cooked and tender.
If the sauce is too thick, stir in a splash of water to reach your desired consistency, and season with salt to taste.
Serve the chicken korma hot over cooked basmati rice, garnished with the reserved caramelized onions, fresh cilantro, and crushed peanuts.