For the filling:
Heat a wok over high heat, and pour in the groundnut oil. Add the chicken pieces, and reconstituted mushrooms, and stir-fry for 1 to 2 minutes, then season with the soy sauce and five-spice powder. Remove the contents from the wok, and set them aside to cool for 10 minutes. Clean the wok.
Add the ginger, bean sprouts, spring onions, and carrot to a bowl. Then, add the chicken and mushrooms, the oyster, and soy sauces and stir to mix. Season with sea salt, and black pepper, to taste.
For the spring rolls: Take 2 spring roll wrappers and lay 1 on top of the other. Cook's Note: The extra thickness will prevent the skin from breaking. Spoon 2 tablespoons of the filling in the center of the wrapper. Brush each corner with the blended cornstarch slurry. Bring the 2 opposite side corners of the wrapper together and, keeping your finger on those edges, bring the bottom corner up towards the middle, then roll the pastry with the filling towards the top corner. Tuck the top edge in, and seal it with the cornstarch slurry. Repeat until the remaining ingredients are used up. Place the spring rolls in the refrigerator to chill until ready to fry.
Heat a wok or heavy-bottomed pan over a high heat, and fill it to a quarter of its depth with enough groundnut oil.
Heat the oil to 350 degrees F, or until a cube of bread dropped in it turns golden brown in 15 seconds.
Deep fry the spring rolls until golden brown, turning frequently, and then transfer them, using a slotted spoon, to drain on an absorbent kitchen towel.
Ensure your wok is stable before deep-frying. For a vegetarian option, substitute the chicken with mushrooms, and use a vegetarian oyster sauce. This recipe would also be great with duck. Check to see if your spring roll wrappers can be eaten raw; there is a brand available which is made from coconut oil and salt.