Shred plantains using the large holes of a box grater.

Heat oil in a large saucepan over medium heat. Add garlic and 1/4 cup cilantro; cook, stirring, until the garlic is softened, 1 to 2 minutes. Add broth and water and bring to a boil. Stir in plantains and reduce heat to a simmer. Simmer until the plantains are tender and the soup is thickened, 25 to 30 minutes. Stir in the remaining 1/4 cup cilantro and season with salt and pepper. Sprinkle each serving with 1 teaspoon Parmesan cheese and garnish with a lime wedge.

Tip: Plantains are usually sold underripe with green-yellow skin - just what you'll need for this recipe. (A ripe plantain, with black-yellow skin, should not be used instead.) Find them at large supermarkets or Hispanic markets. To peel an unripe plantain, slice off both ends and cut into 3-inch lengths. Using the tip of a paring knife, cut 4 lengthwise slits along each piece. Soak in ice water for 3 to 5 minutes to loosen the skin. Remove from the water and peel.