The bread mix infused with sourdough starter. You use this instead of yeast to make a delicious sour loaf of OMG at home. So so good with tomato, eggs, avo, marmite etc. The instructions are in the premix bag, you can keep this alive in the fridge and feed it once a week if you arent using it, of freeze it if you are going away for a few weeks. 

Sourdough Starter