Sourdough starter is essential in order to make and bake sourdough bread. For this you will need:
Flour (preferably organic)
Cling Film or kitchen cloth
To make a starter
Add 50g of flour to 50ml (approximately) of warm water. Mix well, cover with cling film and leave in a dark warm place (e.g. kitchen cupboard) for 24 hours. After that time and for the following days keep feeding (adding) to this mixture every 24h with another 50g of flour and 50ml of warm water. You can keep going with adding these ingredients for as long as you want. Some people have been feeding their starter for a few years. Mine is approximately 6 months old. In order to get a good sour dough bread, your starter must be at least 7 days old. To do this batch you will need a big fermenting bucket or a large bowl, a set of kitchen scales and cling film or a kitchen cloth.