• 300g? (500g seemed like too much) bread toasted (20min at 180C convection)
• 3 litres of water, boiling

Combine and let sit over night (to extract sugars from bread). Filter out the bread.

The next morning, add:

• 200g sugar
• 7g dry active yeast
• Handful of raisins

Let sit at room temperature about 8-10h in covered pot, until foam on top goes away.

Put in a bottle (filtering it), loosely put on lid, put in fridge overnight.

In the morning, tighten lid. Ready the next day. There could be a lot of pressure in the bottle…