Blanch spinach for 1-2 minutes, cool in ice water, and blend with 1/4 cup water into a puree.
Optionally fry paneer until golden or soak in warm water; set aside.
Heat oil or ghee, sizzle cumin seeds, and cook onion until golden, 5-7 minutes. Add ginger-garlic paste and chilies; cook 1 minute.
Add turmeric, coriander, chili powder, and tomatoes; cook until oil separates, 5-7 minutes.
Stir in spinach puree and 1/4 cup water; simmer 5 minutes.
Add paneer, cream, garam masala, and optional kasuri methi; simmer 2-3 minutes. Stir in optional butter.
Serve hot with naan, roti, or rice, with optional lemon.