1. Cut nori in half to form 12 rectangles and have a small bowl of water nearby. Place a piece of nori on a clean work surface, shiny side down. Dip your fingertips in water (to prevent rice from sticking) and place about 3 tbsp rice near 1 of the short ends on a slight diagonal.
2. Make a small indentation in the rice with your finger.
3. Place 1 strip cooked pork (or 2, if small) and 1 slice mango in rice indentation. Add cilantro, if desired.
4. Fold lower corner of nori over, tucking it over and around filling.
5. Continue rolling nori into a cone shape.
6. With wet fingertips, lightly crush a few grains of rice and use to "glue" the end of the nori around the cone. Repeat with remaining ingredients, making a total of 12 rolls. Serve immediately or cover and refrigerate for up to 2 hours. Bring to room temperature before serving.