Step 1

Chop the whole fresh or frozen green tomatoes into small dice and set aside.

Step 2

Cut off the stems and roughly cut up the chillies. Remove the skin and roughly chop the ginger. Peel the garlic cloves.

Step 3

Put the fish sauce into the food processor with the chillies and their seeds, garlic and ginger and blitz into a fine puree.

Step 4

Spoon the puree into a deep, heavy-bottomed pan and add the sugar and wine vinegar.

Step 5

Bring to the boil slowly, stirring as you go. When it comes to the boil, turn down to a simmer and add the diced tomatoes.

Step 6

Skim off any foam that rises to the surface and cook gently for about 1 hour, stirring from time to time, to prevent the mixture catching and burning. Scrape the sides of the pot too, so that everything cooks evenly.

Step 7

The mixture thickens as it cooks when it seems looks thick enough and your wooden spoon leaves a clear trail through the mixture take it off the heat..

Step 8

Use a ladle or jug to pour it into warm, sterilised jars and seal.