Creating Crispy Chilli Beef with Sweet Chilli is straightforward. Follow these steps for an amazing dish:

1. Slice the Beef: Begin by slicing the beef thinly against the grain. This ensures tenderness once cooked.
2. Coat the Beef: In a bowl, mix cornflour, salt, and black pepper. Coat each slice of beef evenly in the mixture.
3. Heat Oil: In a deep skillet or wok, heat enough vegetable oil to submerge half of the beef.
4. Fry the Beef: Add the beef slices in batches and fry until golden brown and crispy, about 3-4 minutes. Remove and drain on a paper towel.
5. Stir-Fry Vegetables: In the same pan, remove excess oil, leaving about a tablespoon. Add sliced onion, red, and green bell peppers. Stir-fry for 3-4 minutes till slightly tender.
6. Prepare Sauce: In a small bowl, mix together sweet chilli sauce, soy sauce, and rice vinegar. Pour the sauce into the pan with vegetables.
7. Combine: Add the crispy beef back into the pan and toss everything together until well-coated.
8. Garnish: Finish off with sliced spring onions and sesame seeds for added flavor and presentation.
9. Serve Hot: Transfer to a serving dish while it’s still hot.

These steps will guide you in preparing an impressive Crispy Chilli Beef with Sweet Chilli that will wow your family and friends.