Creating Crispy Sweet Chilli Beef is easier than you might think. Follow these steps for a delicious outcome:

1. Prepare the Beef: Slice the beef sirloin into thin strips, about 1/4 inch thick. This will help achieve a crispy texture.
2. Coat the Beef: Place the cornflour in a bowl. Dredge the beef strips in the cornflour, ensuring they are well coated. Shake off any excess flour.
3. Heat the Oil: In a large pan or wok, heat the vegetable oil over medium-high heat.
4. Fry the Beef: Once the oil is hot, add the coated beef strips in batches. Fry until golden brown and crispy, about 3-4 minutes per batch. Remove and drain on paper towels.
5. Sauté the Vegetables: In the same pan, add more oil if necessary. Sauté the onion, bell pepper, garlic, and ginger until they are soft and fragrant.
6. Make the Sauce: In a small bowl, mix the sweet chilli sauce, soy sauce, rice vinegar, sesame oil, salt, and black pepper. Stir to combine.
7. Combine Everything: Add the crispy beef back into the pan with the sautéed vegetables. Pour the sauce over the mixture and toss to coat everything evenly.
8. Simmer: Cook for an additional 2-3 minutes, allowing the sauce to thicken slightly and adhere to the beef and veggies.
9. Garnish: Remove from heat and garnish with sesame seeds and fresh coriander.
10. Serve: Plate the dish immediately for the best presentation and enjoy!