Heat the oil in a frying pan, add the garlic and ginger and cook over a medium heat, stirring, for 2–3 minutes. Add the mushrooms and soy sauce and cook, stirring, for 3–4 minutes until golden. Remove from the heat, season with salt and pepper and stir in the coriander. Leave to cool.
Meanwhile, make the dressing. Put all the ingredients in a saucepan and heat over a low heat, stirring, until hot but not boiling. Keep warm.
Put a teaspoon of the mushroom mixture in the centre of each wonton wrapper. Brush a little water around the filling and fold the wontons in half diagonally, pressing the edges together to seal.
Bring a large saucepan of lightly salted water to a rolling boil, add the wontons and cook for 2–3 minutes until they rise to the surface. Gently drain and transfer to warmed serving bowls. Strain over the dressing and serve immediately.