This recipe comes from Fergus Henderson's Beyond Nose to Tail cookbook, and is the precursor of a number of bread recipes from that book. This will work well in place of any sour starter, and has the benefit of being derived from purely natural yeasts.

Note: When you need to use some, don't forget to replenish the mother. Do this by re-adding a combination of 1/2 flour, 1/2 water in the same amount that you removed. Make sure to leave it for a day to ferment before using it again.

Note: You can leave mother in the fridge indefinitely, but you will need to restart it 3 - 4 days before you need it. Do thus by discarding 1/3 of the mixture and feeding it equal parts of flour and water. Repeat daily until you see signs of fermentation.