Add the chopped or grated brown onion, remaining garlic, ginger, and garam masala, along with the cumin, ground coriander, crushed tomatoes, and chilli powder if using into a blender or food processor and blend until nice and smooth. Place in the fridge until ready to use.
2 tsp Ginger, 2 tsp Garlic, 2 tsp Cumin, 1 tbsp Ground coriander, 0.5 tbsp Garam masala, 14 oz Crushed tomatoes, 1 Brown onion, 1 tsp Chill powder