Sourdough starter

 

Day 1: 50 g flour + 50 ml water
Day 2: 50 g flour + 50 ml water
Day 3: Discard 100 g, add 100 g flour + 100 ml water
Day 4: Discard 150 g, add 100 g flour + 100 ml water
Day 5: Discard 200 g, add 150 g flour + 150 ml water
Day 6: Discard 250 g, add 200 g flour + 200 ml water
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Store in fridge if not using daily. To feed, throw away half of starter and replenish with equal masses of flour and water.

Optionally, to turn this into "solid" levain: stand mixer on low speed for 6 min. Cover with plastic wrap, poke centre. Leave at room temperature for 6h then chill overnight.
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When making bread, the first step involves mixing in the starter and then a long rise (~12h). You can then reserve some of the resulting risen mixture as the starter for the next session.
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Some recipe options:
100% rye sourdough (Irish)
Danish (60%) rye bread with sourdough
100% rye sourdough
100% rye sourdough (German)