Blanch the spinach in boiling water for 10 seconds, remove and immerse in cold water to retain the color.
Drain and pureé the spinach in a blender. Heat the butter in a pan, sauté the onions and garlic till the onion is translucent.
Add the flour and sauté till the flour gets a sandy texture. Whisk in 2½ cups of water to the mixture stirring continuously and bring it to a boil till it thickens.
Add in the spinach purée and mix well. Season with salt and pepper and bring to a boil.
Serve hot, garnished with a tablespoon of cream in each bowl.