Heat over a medium-high heat to bring to a boil. Reduce heat and simmer for 5 minutes.
Transfer the mushroom mixture to a mixing bowl and add remaining ingredients. Mix thoroughly to create a thick batter.
Remove from the heat and either store in a glass jar to be used at a later date or pour over stir fry vegetables.
Simmering the sauce for 5 minutes helps to reduce the sauce and intensify the flavors.