For the sauce:
Combine all the ingredients in a heavy based saucepan and gently cook over medium heat until the sugar has dissolved and the sauce has reduced to a syrupy consistency.
For the meat:
Trim and cut the fillet into the desired shape, or leave it as is. Sear the beef in a very hot heavy based griddle or frying pan. When the beef is brown all over, but still rare inside, remove from the pan and allow it to rest for at least 10 minutes before slicing.
In a separate frying pan, heat up some oil and quickly sauté the mushrooms so that they are golden, but still firm. Toss the mushrooms in the reduced balsamic teriyaki. To serve, place the meat onto a plate or serving platter. Top with the mushrooms, drizzle with balsamic teriyaki and garnish with deep-fried vermicelli.
. The sauce can be made ahead of time and stored in the fridge.
. To deep-fry the vermicelli noodles, heat vegetable oil in a deep saucepan. Once the oil is hot enough, add the vermicelli noodles and cook until puffed up. This only takes seconds so be sure to watch them.