Combine garam masala, cumin, cinnamon, coriander, and cayenne in a small bowl and set aside.

Heat a large pan over medium high heat and when hot, add the avocado oil. Add the reserved spices and cook until fragrant, about 5-10 seconds. Add the onion and salt and cook until the onion is soft and translucent, about 5 minutes. Add the garlic and ginger and cook until fragrant, about one minute more. Add the spinach, and 1 cup chicken stock. Bring to a boil and simmer for about 5 minutes.

Add about half of the mixture to a blender and process until smooth. Return this mixture to the simmering pan and continue to cook for another 5-10 minutes.

Remove the mixture from heat and stir in the the heavy cream, if using. Taste and adjust seasoning with more salt, as needed.

While the sauce cooks, make the meatballs. Combine all meatball ingredients in a large bowl and use your hands to mix until evenly combined. Form into about 1 tablespoon size meatballs, about 30 meatballs.

Heat a large nonstick pan over medium-high heat. Add the meatballs and cook until golden, turning occasionally until browned on all sides and cooked through, about 10-15 minutes.

Add the meatballs to the cooked spinach sauce and serve.