The night before baking the bread, mix the rye flour with 450ml of warm water in a large bowl. Add the sourdough starter and stir well. Cover loosely with a plastic bag and leave to ferment overnight.
In the morning remove 75g of the ferment into a covered glass jar and place in the fridge until the next time a sourdough starter is needed.
To the remaining ferment, add the wholemeal & malted flours, salt & seeds, if using. Knead in a stand mixer for ten minutes. The mixture is quite wet, so it's a bit more difficult to do by hand, but entirely possible.
Dust a proving basket with flour, then press the dough into it. Alternatively, form the dough into a freestyle loaf and place on a greased or lined baking tray. As the dough is quite a soft one, a free style loaf will flatten out. For a uniform loaf, place the dough into a 1 kg/2lb loaf tin.
Cover loosely with a plastic bag, ensuring it doesn't touch the dough and leave to prove until the loaf has risen by about ⅓. This could be anything from 2 to 6 hours depending on the temperature of the room and the liveliness of the starter.
Turn the loaf out of the proving basket, if using, onto a greased baking tray. Otherwise, dust with a little spelt flour and slash the top 2-4 times with a sharp knife if liked.
When, or just before, you think the loaf is ready for baking, turn the oven on to 220℃ (425℉, Gas 7).
Place the bread in the oven and turn the temperature down to 200℃ (400℉, Gas 6). Bake for 40 minutes or until the bread sounds hollow when the base is tapped. Allow a further 10 minutes or so if baking in a tin. Place on a wire rack to cool.
Rye sourdough bread tends to be better the day after baking. As soon as it's properly cooled down, wrap it up and leave for the following day. This has the added benefit of softening the crust.Please note: calories and other nutritional information are per serving. They’re approximate and will depend on serving size and exact ingredients used.