Garlic Lamb: Combine the sugar, soy, garlic, cornstarch, and orange zest in a large bowl. Add the lamb and mix well. Cover and refrigerate for at least 1 to 2 hours.
Heat a wok over high heat. When the wok is hot, add 2 tablespoons of the peanut oil and heat until just smoking. Add the ginger, garlic, green onions, and red pepper flakes and stir-fry until fragrant, around 30 seconds.
Add the lamb and stir-fry until well browned, about 5 minutes. Deglaze with the rice wine and bring to a simmer. Stir in the cornstarch mixture and bring to a simmer to thicken. Remove from the heat and set aside to cool.
Drain the rice noodles and roughly chop. Set aside. Wipe out the wok and heat over high heat. Add the remaining 2 tablespoons peanut oil and heat until just smoking. Add the mushrooms, onion, carrot, and bell pepper and stir-fry until the vegetables just begin to soften, but still have some crunch, about 3 minutes. Season with salt and pepper, to taste. Remove the heat and cool.
Combine the cooled vegetables, cooled lamb, reserved noodles, basil, sesame oil, and soy sauce and mix well.
Place 1 egg roll wrapper on a flat surface in front of you with 1 point facing you so the wrapper is in a diamond shape. Make sure the unused wrappers are covered with a damp cloth. Brush all of the edges with egg wash. Place 1 to 2 tablespoons of the filling about 1/3 of the way up the wrapper. Fold the point over the filling. Fold in the sides and then roll up. Press to seal. Repeat with the remaining ingredients. If you are going to hold these for a while before frying, dust with cornstarch so they don't get soggy.
Preheat 3 inches of peanut oil in a deep pot to 360 degrees F. Fry the egg rolls, a few at a time, until golden brown on all sides, about 4 to 5 minutes. Drain on paper towels. Serve whole or cut in half diagonally. If you want the halved rolls to stand up, Cut a small piece off either end with a serrated knife to make a flat surface. Serve with Sweet Chili Scallion Dipping sauce.