Heat the avocado oil (or ghee or butter) in a large thick-bottomed pot such as a Dutch oven over medium-high heat.
Add the ginger, garlic, green chili, and asafetida. Sauté, stirring constantly until fragrant, about 2 minutes.
Transfer the chopped onion, coriander, garam masala, turmeric, and kashmiri red chili powder to the pot. Continue sauteing, stirring occasionally, until the spices are very fragrant, about 10 minutes. If at any time the onion begins browning, reduce the heat to medium heat.
Stir in the heavy cream. Add the chopped spinach to the pot in three batches, stirring very well in between each batch. Allow the spinach to cook down a little before adding more so that the pot isn’t overflowing. Once all of the spinach is in the pot, cover it with a lid for a few minutes to encourage it to cook down.
After the spinach has wilted, transfer the saag to a blender or a food processor (or use an immersion blender). Blend to your desired consistency. Pour the saag back into the pot and add the chopped paneer cubes. Heat for a few minutes until the saag paneer is hot.
Serve saag paneer with steamed white rice or brown rice and naan bread.