Thaw the spinach, put in a food processor, and process to a fine purée. Set aside.
Place a nonstick saucepan over medium heat and add the oil. When small bubbles appear at the bottom of the pan, add the peppercorns, bay leaves, cloves, and cardamom, and sauté for 1 minute. Add the onions, chopped ginger, and garlic, and sauté, stirring continuously, for 4 minutes