In a medium bowl, combine beef, salt, and egg, and mix well. Cover and set aside for 15 minutes.
In a heavy-bottomed pot or dutch oven, heat about 1 inch of vegetable oil to 350F over medium high heat. When the beef is done marinating, coat the beef slices with cornstarch, remove any excess cornstarch, and fry in batches until golden brown. Transfer to a paper towel lined plate to drain excess oil.
Heat vegetable oil in a large wok or skillet over high heat. Add garlic, onions, pepper, and cook for 2 minutes.
In a medium bowl, whisk together soy sauce, ketchup, hoisin sauce, rice vinegar, sweet chili sauce, brown sugar, cornstarch, and water. Stir in the sauce mixture, stirring continuously, until the sauce has thickened.
Return the cooked beef to the wok and toss to coat well. Serve immediately.