Roughly chop the onion, garlic, carrot and ginger and add to a blender with a tablespoon of sunflower oil. Blitz to a paste. I prefer my sauce smooth, but if you want the sauce chunky then you don't have to blend it quite so much.
Add this paste to a saucepan and fry over a medium heat for around 4-5 minutes
Sprinkle in the curry powder, spices, white pepper and salt to the paste and stir to combine for a minute or so.
Add the butter and allow to melt, stir through.
Gradually add the stock until combined and simmer for 10 minutes or until the sauce is to your desired thickness.
When the sauce is thick after simmering, add the tomato ketchup and worchestershire sauce. Taste and season with salt and/or pepper, to your liking.