Soft Manioc Polenta

INGREDIENTS

• 1/4 cup finely chopped fresh cilantro
• 2 tablespoons chopped yellow bell pepper
• 2 tablespoons finely chopped fresh flat-leaf parsley
• 1 garlic clove, chopped
• 1 medium onion, chopped
• 16 to 20 shrimp shells (from 1 pound extra-large shrimp; optional)
• 2 (1-inch-thick) slices yellow plantain, peeled
• 1/4 teaspoon salt
• 4 cups water
• 4 sprigs fresh flat-leaf parsley
• 5 sprigs fresh cilantro
• 1 tablespoon fresh lime juice
• 1 pound tomatoes, quartered
• 1 cup toasted manioc flour
• 2 pound heads and bones from white-fleshed fish
• 1/4 cup chopped green bell pepper
• 1 teaspoon salt