You will need a large jar with a lid that will fit about 2.2L of liquid or more for this recipe.
Place coffee into the Thermomix bowl and mill 20 sec/speed 8. Your coffee shouldn't be super fine, so the time may depend slightly on your coffee beans. Tip into the large jar.
Add the water to jar and give it a good stir with a spatula. Seal the jar and leave on the bench at ambient room temperature for 24 hours minimum, an extra day is also ok.
Strain the coffee well, I use a nut milk bag for best results. Return the liquid to the cleaned jar. (Use the solids as garden mulch, my herb garden has never been so fine!)
Add the raisins, sourdough starter, and 1 tbsp of the sugar to the jar and stir to combine. Seal the jar and leave on the bench for 5 days, opening and adding an additional tbsp of sugar every day.
When you open the jar by the 5th day you should be getting a slight fizz and also there should be bubbles rising in the liquid when you open the jar.
Strain and divide between 1 litre glass bottles with a pop top lid (available at Kmart for way less than a kitchen store) and you can further ferment another 1-2 days on the bench. A great way to know that you are getting good fermentation is by using the raisins. Once they float to the surface, you can assume you have good fizziness. You should burp the bottles a couple of times a day so as to avoid the possibility of a kitchen explosion.
Try this on its own or use in our drink suggestions. It is really a great way to get your coffee fix without dairy if that is your thing.