Heat a large Dutch oven over medium heat and add the ghee or oil. Add the cumin seeds and allow to sizzle for a few seconds. Add the onions and cook, stirring frequently, until softened and translucent, about 10 to 15 minutes or until golden brown for a deeper color and flavor.
Add the green chillies if using along with minced garlic and ginger. Saute, until fragrant—about a minute.
Add the ground spices-coriander, nutmeg, turmeric and ½ the Garam Masala.. Cook, stirring frequently for a minute. Next add the tomatoes, stir and bring it up to a light boil.
Add the chicken, turn up the heat, stir and cook until it is no longer pink, about 5-7 minutes. Add about ¼-½ cup of water and stir to combine. Bring it back up to a boil and simmer for about 10 minutes so the chicken is fully cooked.
Stir in the chopped spinach into the pot and mix well. Cover the pot and simmer for about 4-5 minutes or until the spinach is wilted and mixed well with the chicken curry. Stir in the remaining garam masala , crushed fenugreek leaves and add the lemon juice. Heat through, taste and adjust the seasoning as needed.
Enjoy with any flatbread like chapati, naan, pita or basmati rice.