Dust fish fillets with cornstarch and a pinch of salt.
Heat 2 tbsp oil in a pan and shallow-fry fish fillets for 4 minutes on each side until golden and crisp; remove.
Heat remaining oil, sauté garlic paste and chopped green chili for 1 minute.
Add soy sauce, sugar, vinegar, and water; simmer until sauce turns thick and glossy.
Spoon sweet chili glaze over crisp fish fillets and garnish with sliced spring onions.