Heat 1 tbsp vegetable oil in large frying pan over medium heat. Add 1 chopped onion, 2 crushed garlic cloves, 2 tsp grated ginger, 1 tbsp coriander, 1 chopped red chilli, and cook for 4 minutes or until golden.
Stir in 400g chopped tomatoes and 2 tsp fish sauce. Cook for 5 minutes or until slightly thickened. Set aside to cool.