In a bowl, marinate the beef with salt and pepper for about 10-15 minutes.
Using a separate bowl, combine soy sauce, worcestershire sauce, brown sugar and red chili flakes. Stir until the sugar is dissolved then set aside.
In a pan over medium heat, add the butter and add olive oil. Melt the butter then add the garlic. Continuously stir for a minute or until the garlic turns golden brown. Be careful not to burn it.
Add the marinated beef and cook for 1-2 minutes on each side.
Pour the soy-worcestershire sauce mixture and let it cook for another 3-5 minutes. Transfer to a serving plate and enjoy with rice.