Heat 1 tablespoon vegetable oil over medium-high heat, and add garlic and ginger. Stir-fry until fragrant but not browned, about 30 seconds, then add carrot, cabbage, green onions, mushrooms, and salt. Sook, stirring, for a few minutes or until the vegetables just start to soften up and lose their rigidity.

Stir in sesame oil and oyster sauce, and cook for 1 minute more; reduce the heat to medium-low. Add the uncooked vermicelli noodles, and use tongs to cover noodles with hot vegetable mixture. The noodles will quickly loosen up and separate; continue to use tongs to toss and stir everything until uniformly mixed.

Transfer mixture to a bowl, and add peas, ham, cayenne, and black pepper. Mix thoroughly to combine. Taste for seasoning, and add more salt if desired. Let mixture cool, then wrap and transfer into the refrigerator until ready to use.

Place 1 egg roll wrapper on a clean work surface, and position it in a diamond shape. Paint egg wash on all 4 edges. Spoon about 1/3 cup of filling on the bottom third of the wrapper. Make sure it’s centered and evenly distributed. Fold the bottom tip of the wrapper up and over the filling and roll once to cover filling. Fold in sides, making sure to cover filling and align sides nice and straight. Finish rolling egg roll up, ending with the tip and seam at the bottom. Repeat with remaining wrappers and filling.

Heat oil in a deep-fryer or large saucepan to 350 degrees F (175 degrees C). Fry egg rolls until browned and crisp, 4 to 5 minutes. Drain on a paper towel-lined plate and let rest for a minute or two before serving.

Optional: Whisk mustard, rice vinegar, and sriracha together in a small bowl. Serve egg rolls with mustard sauce, or other prepared egg roll sauce.