Heat the ghee in a large non-stick skillet over medium heat and add the paneer cubes, searing until golden brown on all sides, then remove and set aside.
In the same skillet, add the diced onion, minced ginger, and minced garlic, sautéing for 3-4 minutes until the onions are translucent and fragrant.
Stir in the turmeric, cumin, garam masala, sea salt, and black pepper, toasting the spices for 1 minute to release their oils.
Add the fresh spinach to the skillet with a splash of water, covering with a lid for 2 minutes until completely wilted.
Transfer the spinach and onion mixture to a high-speed blender, add the Greek yogurt, and pulse until the sauce is smooth and vibrant green.
Pour the sauce back into the skillet over low heat, stirring in the cooked brown lentils and the seared paneer cubes.
Gently simmer for 3-5 minutes until the curry is heated through, being careful not to boil the yogurt sauce, and serve immediately.