Add one teaspoon olive oil to a large stainless steel pot and heat over low heat, then add the mustard seeds and cumin seeds. Roast the seeds for 20 seconds.
Add the cardamom and cloves, roast them for 1 minute, stirring frequently.
Remove from heat and grind into a powder in a grinder.
Add the remaining oil to the pan. Sauté the onlon on medium heat. As the onion begins to brown add the garlic, continue to sauté until both onion and garlic are golden brown.
Add the sweet potato and sauté an additional 3 to 4 minutes, then add turmeric, cinnamon, and black pepper, along with the powdered spices you roasted earlier.
Add the coconut milk and spinach, and let cook for 15-20 minutes, until the sweet potatoes are very tender.