Start by cutting the chicken breasts into bite-sized chunks, ensuring uniform pieces for even cooking. Season the chicken generously with salt and pepper, then toss it in cornflour until fully coated. Set the chicken aside while you prepare the sauce.

In a medium bowl, combine the canned pineapple juice, soft brown sugar, dark soy sauce, and tomato purée. Whisk the ingredients together until the brown sugar dissolves completely. Set the sauce aside for later.

Heat 2 tablespoons of vegetable oil in a large wok or frying pan over medium-high heat. Add the seasoned chicken pieces in a single layer and stir-fry for about 5-7 minutes, until golden brown and cooked through.

Reduce the heat to medium and add finely chopped onion, sliced red bell pepper, minced garlic, and grated ginger to the wok. Stir-fry the mixture for another 3-4 minutes, until the vegetables start to soften.

Pour the prepared sauce over the chicken and vegetable mixture in the wok, adding in the chopped pineapple. Stir everything together, allowing the sauce to envelop all the ingredients. Cook for an additional 2-3 minutes.

Spoon the Sticky Pineapple Chicken over a bed of cooked rice, garnish with fresh coriander and drizzle with Sriracha. Serve immediately.