Prepare the vegetables: thinly slice the onion, carrot, and king oyster mushrooms. Finely chop the green onions.

Heat oil in a pan. Add all the sliced vegetables and stir-fry until cooked. (Note: Mushrooms release water when cooked, so stir-fry over high heat until the mushrooms are cooked and dry. Let the mixture cool. Once cooled, transfer to a bowl, add the ground chicken, green onions, salt, black pepper, sugar, and chicken bouillon powder. Mix well, then start wrapping the spring rolls.