Wash palak, put it in a pot,add salt and water, boil until just soft. Keep aside.
Heat 1 tbsp butter in a another pot, add jeera, garlic, cinnamon, green chillies, and onions, braise till garlic and onions turn golden brown. Put this in grinder with boiled palak (dont throw away the water in which the palak is boiled, you can use it for grinding or cooking). Grind into smooth paste.
Heat the remaining butter in a pot, add palak and paneer cubes, reduce the heat and cook for 15 mins.
Add milk, and cook again for 10 mins till thick.
Garnish with onion rings and slitted green chillies.