There are may web pages about making your own starter but really the best thing to do is to find someone who bakes good sourdough and ask them for a bit of theirs. Most will be more than happy to give you some - and you only need a couple of tablespoons of starter to get you going. It will take a little while for the starter to get used to your new regime but within a couple of weeks you should have your own healthy sourdough starter. Most of the bread I make uses at least 50% white flour so that's what I use to feed the starter. The starter will get used to your particular flour so once you've chosen one, stick with it. In the UK I found that both Shipton Mill and Doves Farm untreated organic white worked well.
It's a bit of a bind but you will get the best results if you feed your starter daily. For each feed, take 10g of the old starter and add 20g of flour and 20g of water. Discard the remaining old starter, mix the new one and store covered at room temperature. Small jam jars or ramekins with a loose cover are perfect for storage. Keeping such a small amount of starter (50g) means you will have minimal waste each day but you won't have enough to bake with. When you want to bake you will need to plan ahead and bulk up your starter - bearing in mind that 50g will make 250g in one feed and 1.25kg in two feeds. If your starter is in good health you will be able to feed it twice in the 24 hours before baking but better to play safe and do it daily. If you are in a hurry you can place it somewhere warmer to speed its development.
Depending on conditions, the starter will be at it's best between 6 and 10 hours after feeding. The ideal time to use it is when it is fully risen and still has some structure; before it begins to look frothy with wet bubbles and liquid flour and water. At this point there will be plenty of lively, active yeast cells just waiting to feed on your dough.
Starter will be quite happy left 2 or 3 days at room temperature. Any longer and you'll want to put it in the fridge where it will keep for at least a month. It is possible to keep it in the freezer but I haven't tried and frankly it might be better to visit your baker friend again if you want to leave it that long. After being left for any amount of time the starter will need consistent daily feeding for at least a few days to bring it back to good health before baking with it again.
First mix all of the flour, water and starter into a fairly consistent gooey mess. Don't add salt yet. This is best done in a large mixing bowl. Cold water is fine unless your room is cold in which case you might want to use slightly warmer water.
Cover and leave for about an hour. Some bakers will have only mixed the flour and water at this stage but I found little difference by adding the starter into the mix and it's a lot easier to mix in the starter before the autolyse. This is when the water gets to work softening the dry flour and helps with gluten development. Temperature isn't so important but don't let the dough become too cold as it will take longer to rise.
Wet a surface with a damp cloth and tip out the dough. Add the salt and any other ingredients you want to use. I knead using a stretch and fold method. Push the heel of one hand firmly into the centre of the dough and push away from you while holding it in place with the other hand, stretching it out to around twice its length. Then take the far end and fold it back over onto itself. Rotate one quarter of a turn and repeat. And repeat. I do this about 50 times for the first knead. If the dough sticks to your hands or surface too much, scrape off, dampen your hands and continue. Using flour to prevent sticking will upset the consistency of the dough. With a little practice you'll be able to handle the dough without getting yourself covered in it. You should have a good pliable dough at this point. Put it back in the bowl and leave for 30 minutes.
From this point onwards you want to maintain the structure of your dough. Try not to tear it too much and look after the bubbles that the yeast is making - they're what give the bread its rise.
Prepare your surface as before, tip out the dough and stretch and fold 10 - 15 times. Be firm but gentle. You want to stretch the dough but not break it. Put it back in the bowl and leave for a further 30 minutes.
Same as the second. Place in the bowl and leave for an hour.
Same again. Leave for another hour.
Dampen your surface again and divide the dough into as many loaves as you need. To make a round loaf, flatten the dough a little with the heel of your hand, gently stretch the far end away from you and fold it back into the centre. This is similar to the stretch and fold but more gentle. Turn about a quarter of a turn and repeat. Do this a few times and you will feel the dough becoming firmer and the outside (underneath) becoming taught and resistant to stretching. At this point, turn it over onto a dry surface and pull it towards you with both hands behind and slightly underneath. This further tightens the top of the loaf. Finally, turn it over again and put it top-side down into a floured banneton or mixing bowl lined with a floured cloth. Cover with cling film or a damp cloth and leave somewhere warm for 2 hours to prove. It can also leave it in the fridge overnight. Slightly under-proved is better than over or you may find your bread collapsing in the oven.
Preheat the oven to about 230 degrees, maybe 210 for a fan oven. Find a peel of some sort - a chopping board or the base of a large cake tin will work well - anything that you can use to slide the loves into the oven. Dust the peel with semolina or some coarse flour. Turn out the loves onto the peel, slash them with a sharp knife (a craft knife is perfect) and slide them, ideally onto a baking stone but a baking tray will do, in the oven. Bake for 30-35 minutes.
If your oven is a fan oven the loaves won't rise so well. This is because the hot air blasted onto the crust causes them to dry and set too quickly. You can overcome this by using a Dutch oven: preheat a large metal pot with a lid in the oven and put your loaves into this, lid on for the first 20 minutes, to bake.
To make 2 loaves of about 600g:
- 750g flour (at least 50% strong white)
- 445g water
- 150g starter (remember to save some to feed up for the next bake)
- 12g salt
I've honed this procedure over a few years and it works well for me. I tend to stick with either a standard white loaf (with about 30g wholemeal per loaf) or a malted loaf which is 50/50 strong white and malted grain flour. It takes a while to get used to the feel of the dough and develop your ability to handle it. You may need to adjust the amount of water slightly, play around with temperatures and kneading times until you've got a reliable basic loaf. By which time you may feel the need for more adventurous flours and other dry ingredients, perhaps some oil, but with bread that tastes this good, you may not bother. One last thing, sourdough keeps for at least a week at room temperature in an airtight container so don't be tempted to keep it in the fridge where it will quickly go stale.