Prepare Tuna Balls: In a bowl, combine drained tuna with cornstarch, flour, ginger-garlic paste, soy sauce, pepper, and salt. Mix well and form into small, tight balls.
Fry: Heat oil in a wok and deep fry or shallow fry the tuna balls over medium heat until golden and crispy. Set aside.
Prepare Sauce: Heat 2 tbsp oil in a pan. Add garlic, ginger, and green chilies. Sauté until fragrant. Add onions and bell peppers, stirring on high heat.
Add Sauces: Add soy sauce, chili sauce, vinegar, and sugar.
Thicken: If you prefer gravy, add cornstarch slurry (1 tsp cornstarch + 2 tbsp water) and cook until thick.
Combine: Add the fried tuna balls to the sauce and toss well to coat
