Brown the beef on both sides in small batches, just to colour the beef. DO NOT let it cook through. Set aside.
Deglaze the pan with 1 tbsp of rice vinegar and a bit of water. Make sure to get all the beef that is stuck to the bottom. This will give your dish real depth of flavour.
Add the rice vinegar, oyster sauce, soy sauce and sweetener if using, cook until it thickens.
Add the peppers and baby corn, cook for a further 2-3 minutes. Serve and enjoy!