Place all the ingredients into a pot with high sides and stir to combine.
Bring the mixture to a boil over medium heat.
Once it starts boiling, cover the pot with a lid and turn the temperature down slightly.
Simmer over medium heat for about 12 minutes until nice and thick.
You can then add more water and let it simmer a little longer to give it a deeper flavour (I don't do this).
Leave to cool and store in a glass jar in your fridge.