Prepare ingredients: finely chop garlic, chicken, shrimp and soaked shiitake; slice yam bean and carrot.
Heat 3 tablespoons oil in a wok over medium heat. Add garlic and stir-fry until fragrant, about 30 seconds.
Add the chopped chicken, shrimp and mushrooms and stir-fry until proteins are cooked through, about 3–5 minutes.
Add the sliced yam bean and carrot and stir-fry 1–2 minutes, then pour in 1 cup water and cover; simmer 15–20 minutes until vegetables are tender.
Stir in chicken stock granules, salt, pepper and oyster sauce. Add the cornstarch mixture and cook until sauce thickens and coats the filling; remove from heat and let cool.
Make a sealing paste by mixing 2 tablespoons plain flour with 4 tablespoons water until smooth.
Place a spring roll wrapper on a flat surface. Spoon about 2 tablespoons (two spoonfuls) of cooled filling into the center, fold in the sides, roll up tightly and seal the edge with the flour paste. Repeat with remaining wrappers and filling.
Heat enough oil in a wok to about 2 cup depth to 350°F (175°C) or medium heat. Fry popiah in batches until golden brown and crispy, turning as needed, about 2–4 minutes per batch.
Drain on paper towels and serve hot with chili sauce if desired.