Soak the dried shiitake mushrooms in warm water until rehydrated. Soak the noodles according to the package instructions. (Usually 3-4 minutes in hot, boiling water.) Mince mushrooms when they are rehydrated and chop the noodles into about 1-inch pieces as well.
Shred or shave cabbage and carrots. Smash and mince garlic cloves and mince cilantro stems.
Measure remaining ingredients and set everything aside.
Make sure to thaw spring roll wrappers if they are frozen.
Prepare the filling:
Preheat a large wok (or a deep, large cooking pan) and drizzle some canola oil.
Add minced garlic and sauté just for a few seconds, until fragrant. Add ground pork and break it up and add about a tablespoon of soy sauce. Keep cooking and breaking it up until almost done.
Add in cabbage and carrots, stir and cook until both softened. Stir in minced cilantro stems and minced shiitake.
Stir in remaining soy sauce, oyster sauce, sugar, and peppers. Stir well and finish cooking until vegetables are completely softened.
Take off heat and let it cool to room temperature before rolling.
Wrapping spring rolls:
Whisk the egg in a small bowl and set it on your work station.
Place a spring roll wrapper on a diamond.
Spread about 3-4 tablespoons of filling in a line, on the lower part of the diamond, leaving about a couple inches on each side.
Gently and carefully, fold the bottom corner over the filling mixture. Fold both side corners toward center of wrapper, it will start to look like an open envelope.
Dip your fingers in the egg and run it all along the edges of the wrapper to seal better. Carefully roll up the spring roll. Repeat with remaining spring rolls.
Frying Spring Rolls:
Place a couple of sheets of paper towel onto a wire rack for the spring roll when they're fried.
Preheat canola or vegetable oil to 350° and fry a few spring rolls at a time (don't overcrowd them). Fry spring rolls for 5-6 minutes, until golden-brown. Use metal tongs to take the spring rolls out and place them onto the prepared wire rack.
Air-frying spring rolls:
To air-fry spring rolls, place them into the air-fryer basket in one layer and make sure to give them a little space between. Don't overcrowd.
Air-fry spring rolls at 375° for 12-14 minutes, until crispy golden brown.
Baking spring rolls:
Preheat the oven to 400° and fit a wire rack inside a baking sheet. Lightly grease the wire rack.
Place wrapped spring rolls onto the wire rack and bake for 18-20 minutes.
Serve Thai spring rolls with Sweet Thai Chili Sauce.