Step 1: In a medium bowl, combine the bite-sized chicken pieces with the plain yogurt, turmeric powder, red chili powder, and a pinch of salt. Mix thoroughly to ensure every piece is coated. Let the chicken marinate at room temperature for at least 30 minutes, or for an even richer flavor, cover and refrigerate overnight.
Step 2: Heat the vegetable oil or ghee in a large heavy-bottomed skillet or pot over medium heat. Add the finely chopped onion and sauté, stirring occasionally, until it becomes soft and beautifully golden brown, about 5-7 minutes. Stir in the minced garlic and grated ginger, cooking for another 1-2 minutes until fragrant.
Step 3: Add the marinated chicken to the skillet, cooking until it browns on all sides, approximately 5-6 minutes. This helps to seal in the juices. Next, sprinkle in the garam masala, ground cumin, and ground coriander. Stir well and allow the spices to toast lightly with the chicken for about 1 minute, enhancing their aroma.
Step 4: Pour in the full can of coconut milk, stirring to combine all the ingredients with the chicken and spices. Bring the mixture to a gentle simmer. Once simmering, reduce the heat to low, cover the pot, and let the korma cook for 20-25 minutes, or until the chicken is fork-tender and the sauce has thickened slightly. Stir occasionally to prevent sticking.
Step 5: Once the chicken is cooked through and the sauce has reached your desired consistency, taste the korma and adjust the seasoning with additional salt or red chili powder if needed. Remove from heat. Just before serving, generously garnish with fresh chopped cilantro for a vibrant finish.