Preheat oven to 180°C/350°F/gas 4
In a large wok, heat the oil and stir-fry the carrot for a minute.
Add in the cabbage, mushrooms and chicken and fry for another minute, stirring continuously.
Season with white pepper and add the sugar, soy sauces and sesame oil.
Combine two teaspoons of the cornflour with 3 tablespoons of water and stir into the filling while still on the heat, the juice will thicken. Leave the filling on one side to cool.
Mix the rest of the cornflour with enough water to make a thin paste. Place a spring roll wrapper on the counter and put a tablespoon of the cooled filling across one end. Brush the wrapper edges with the cornflour liquid. (The cornflour mixture will help keep the edges stuck together).
Fold the two opposite edges of the wrapper over part of the filling and roll into a tight cylinder.. Pinch the edges together so that you have a good seal.
Transfer to a baking sheet. Repeat with remaining sheets, then brush with a little more butter. Bake for 15-20 mins until golden and crisp. Serve with a sweet chilli dipping sauce.