Using a sharp knife, dice the chicken into 1/4in pieces. Heat the groundnut oil in a wok over a high heat and stir-fry the chicken for 2-3 minutes, stirring all the time.
Season with soy sauce and sprinkle with five spice powder before taking the chicken out of the wok and leaving on one side to cool.
In a large bowl, mix the mushrooms, garlic, ginger, beansprouts, scallions, and sliced carrot. Add the cooled chicken and stir well to combine everything together.
Place two spring roll wrappers on top of each other, and spoon two tablespoons of the chicken filling in the centre of the layered sheet.
Mix the cornstarch with the water and use to brush over the wrapper edges - this helps stop the spring rolls from bursting open while frying. Fold each of the opposite corners in, over the filling, and roll the wrapper into a cigar shape.
Deep fry the spring rolls in hot oil, over a medium heat, until golden brown - about 3-5 minutes. Drain on absorbent paper before serving with sweet chilli sauce.