Combine the chicken, spring onions, soy sauce, oyster sauce, Chinese wine, stock powder and white pepper in a bowl. Toss well, cover and refrigerate for at least 20 minutes (or up to 24 hours).
Tear the ham into roughly 20 pieces and keep chilled. In a small bowl, mix the flour with enough water to make a thick paste. Set aside.
Working one wrapper at a time, gently separate it and place it in a diamond shape (shiny side out). Add a few slices of chicken and a piece of ham to the bottom corner. Fold the corner over the filling, fold in the sides, then roll tightly. Brush a little flour paste on the final corner to seal. Repeat until you have 20 rolls and keep chilled.
Heat oil in a wok or deep saucepan to 160°C, filling it about one-third up the sides. (To test the heat, drop in a cube of bread — it should crisp in about 20 seconds.)
Fry 4–5 rolls at a time for 4–5 minutes, or until lightly golden and crisp. Drain briefly on paper towel, then transfer to a wire rack. Allow the oil to return to temperature between batches.
Increase the oil temperature to 180°C. Fry the rolls again, in batches, for 1–2 minutes until deep golden and fully cooked. Test one to make sure the chicken is cooked through.
Enjoy immediately with my Chinese Sweet & Sour Dipping Sauce or your preferred dipping sauces.