Heat the ghee/coconut oil on a medium-high heat and add the chopped leek, garlic and ginger. Stir for 3-4 minutes.
Add the cumin, coriander, turmeric, salt, pepper, fennel and hing. Cook for 2 minutes, stirring.
Add kale/spinach along with 170ml water, stir and put on the lid. Cook for about 7 minutes, stirring occasionally. If you are using only spinach, reduce the cooking time to just 2 minutes.
Remove from the heat and allow to cool for a little bit so blending is safe. Either use a wand blender to blend to a rough blended sauce or if you prefer a smooth sauce (perfect for children), remove from the pan and blend for a minute or two in a nutribullet/nutrininja type blender and return to the pan.
Add the paneer and the potatoes, stir into the sauce and simmer on low for 30 minutes, stirring occasionally or until the potatoes are cooked. You may need to add a little more water but don't over do it.
Serve with spelt naan, spelt chapatti or spelt pitta breads.