Chop onion and tomato, mince garlic, peel and grate ginger. If using a bunch of large-leaf spinach, chop about an inch off of the end of spinach stems and submerge in a large bowl of cold water and rinse well. Leave in the water until needed.
Heat a large pot over medium-high heat. Add olive oil and saute onion, tomato, garlic, and ginger for 5 minutes, until translucent.
Add spices: coriander, cumin, garam masala, turmeric, and cayenne pepper. Alternatively, 2 1/2 teaspoons of curry powder can be substituted for the coriander and turmeric in a pinch. Mix well to evenly coat onion mixture in spices.
Next, add 1/2 cup of water. Remove spinach from the rinsing bowl and add to the pot. Stir a bit, then cover. Keep covered, stirring every minute or so, until spinach has fully wilted.
Remove from the heat and allow to cool for 5 - 10 minutes before blending. Blend well, adding up to another 1/2 cup of water to aid with the blending process. Pour back into the pot and place back on the heat and add salt.
Rinse and drain chickpeas/garbanzo beans and add to spinach mixture. Bring to a boil and simmer for a few minutes. Add 1/2 cup of Greek yogurt and mix well.