Pre-heat a large non-stick frying pan on medium to high heat. After a minute add the olive oil, onion and bell pepper. Sauté for 4-5 minutes until the veggies become fragrant and slightly brown in colour.
While the veggies are cooking, add the remaining ingredients except the cheese into a mixing bowl and stir well.
Put the onion bell pepper mix into a small bowl and set aside. Drizzle a bit of olive oil into the same frying pan and pour half of the omelette mix into the pan. Tilt the pan to help the mixture spread evenly into a circular shape. You want the omelette to be thin but not too thin otherwise it will break.
On one side of the omelette, add half of the sautéed onion and bell pepper mix as well as one handful of cheese. Fold the side that has no filling over the side with the filling and gently press the spatula down to flatten the omelette.
Repeat the process to make a second omelette. Serve with a drizzle of garlic aioli, and top with some Sango bean sprouts and black sesame seeds (this is optional).