"Making rye bread needs some planning, as you have to start by making a sourdough starter. Read the whole recipe carefully before you start."-Trine Hahnemann
To make the rye sourdough starter, mix the buttermilk and rye flour well in a bowl, cover and leave at room temperature for 3 days. It’s important that it doesn’t develop mold, but starts bubbling, and a temperature of 23–25ºC/73–77ºF is ideal for this.
If making your first loaf from the starter, dissolve all the starter in the lukewarm water in a large mixing bowl (for the next loaf use just 3 Tbsp of the starter; the whole quantity of starter is just for the first attempt, and the loaf will be a little bigger). Stir in the salt and rye flour, cover the bowl with a tea towel and leave at room temperature for 12–24 hours. After you have taken out the 3 Tbsp for the next rye bread you are going to make, this starter does not need taking care of. Just let it rest in the refrigerator until next time you need it.
Add the cracked rye and cold water to the dough mixture and stir with a wooden spoon until smooth. It will be too runny to knead. Remove 3 Tbsp of the mixture to an airtight container and refrigerate; this will become your sourdough starter for the next loaf you make (it will need to rest for at least 3 days before you use it, and will last up to 8 weeks).
Lightly oil a large loaf tin, about 30 x 10cm/12 x 4in and 10cm/4in deep. Pour in the dough, cover with a damp tea towel and leave to rise for 3–6 hours, or until the dough has almost reached the top of the tin.
When ready to bake, preheat the oven to 180°C/350°F/gas mark 4. Bake the loaf for 1 hour 45 minutes then immediately turn the loaf out of the tin onto a wire rack to cool. This is great to eat just out of the oven, but as it’s difficult to cut, it’s better the next day… if you can wait!