Slice the sirloin thinly across the grain, cutting it about 3 mm thick. To make slicing it easier, you can put the meat in the freezer for 15 minutes so it will become firmer.
Blend the rest of the ingredients minus one tablespoon of the sesame oil in a blender until pureed evenly.
Pour the marinade over the sliced meat and mix until each slice is evenly coated.
Let the meat marinade for about 20-30 minutes.
Heat a large frying pan on medium heat with the remaining tablespoon of sesame oil.
Removing as much of the marinade from the meat as possible, stir fry the meat until mostly cooked through.
If you prefer a lot of juice with your bulgogi, keep it on medium heat allowing for some liquid to be left in the pan (some people like to mix this into their rice). Alternatively, turn up the heat to high for a few minutes until slightly browned and all the liquid is evaporated.
Garnish with sesame seeds and serve with lettuce leaves, kimchi and steamed sticky rice.