For the sauce: Stir together cornstarch and water and set aside. Place sugar and vinegar into a medium pot and simmer until sugar dissolves. Stir in garlic, ginger, chile sauce, and cornstarch slurry (giving it another stir before adding, if contents have settled to the bottom). Allow mixture to simmer for 1 to 2 minutes or until mixture slightly thickens. Remove from heat and allow sauce to cool completely. Sauce will continue to thicken as it cools.
For egg rolls: Fill a tall pot with 3 inches of oil and preheat to 350˚F.
Place all filling ingredients into a large mixing bowl and mix together until very well combined. Allow mixture to sit for at least 30 minutes to allow flavors to merry.
Place a single egg roll wrapper onto a clean surface and brush the surface with a light layer of egg wash.
Take one corner of the wrapper and fold it about ½ way up to the opposite corner and press down to smooth and seal.
Place about 2 tablespoons of filling into a narrow log onto the overlapped portion of the wrapper. Take both sides of the wrapper and fold them in, towards the center of the log of filling.
Brush the ends of the wrapper with more egg wash and tightly roll each egg roll until completely closed and sealed. Place onto a parchment lined baking sheet, seam side-down. Repeat until all the filling and wrappers have been used.
Carefully drop 3 to 4 egg rolls into the hot oil at a time and fry for 5 to 6 minutes or until golden brown and filling has just cooked through. Drain onto paper towels for 1 minute before transferring onto a baking sheet, lined with a cooling rack. Repeat until all egg rolls have been fried.
Serve immediately with sweet-spicy chile sauce.