In a mixing bowl, add minced chicken, sesame oil, mushroom sauce, soy sauce, and ground pepper. Combine them well and leave at room temperature for about 5 minutes.
Add the chopped spring onion and stir to combine. Reduce the heat and allow the filling to cool to room temperature for about 10 minutes or until it is no longer hot.
When the filling is ready and no longer hot, place a rice paper wrapper on a cutting board. Add a spoonful of the filling in the middle of the rice paper. Fold the bottom half up to cover the filling, then fold the sides in from both sides.