Blitz ginger, garlic, and half an onion into a smooth paste using a food processor. Reserve 2 tablespoons of this aromatic mix for cooking later. Combine the rest with dark soy sauce, chili powder, black pepper, and water to create a marinade.

Cut the boneless chicken into 1-inch pieces and add them to the marinade. Cover and refrigerate for at least 1 hour.

In a separate bowl, whisk together tomato paste, oyster sauce, sugar, dark soy sauce, rice vinegar, chili powder, and water. Set aside.

Remove the marinated chicken from the fridge and sprinkle cornstarch over it. Toss to coat evenly.

Heat oil in a wok or fryer to 350°F (177°C). Use a thermometer to ensure proper temperature.

Fry the coated chicken in small batches for 5-6 minutes until golden brown and crispy. Drain excess oil.

In a separate pan, heat oil and sauté the reserved ginger-garlic-onion mix until fragrant. Add red pepper and stir-fry for 2 minutes.

Pour the prepared sauce into the pan with the aromatics and simmer for 2-3 minutes.

Add the fried chicken to the sauce and toss to coat. Cook for an additional minute.

Garnish with cilantro and serve over rice or noodles.