Sourdough

Danish original recipe: http://www.gastro.dk/opskrifter/tilbehor/meyers-surdej/

9dl water
150 g plain flour
75 g grahams flour
75 g rye flour

Put all ingredients together in a bowl and mix together. Leave for 10 days in a jar or bowl, a bit open so it can breathe, stirring once a day only.
After 10 days the dough should smell like a dark, good beer.