I brew a fair bit of beer and at the end I get a couple of kilos of yeast that's dropped out of suspension.
I usually wash it down the drain or stick it onto the compost heap.
But occasionally I make bread with it.
For this recipe, you'll need:
1 table spoon of olive oil
1 tsp of salt
500g of strong flour. I used a mix of white and brown because its all that was left in the cupboard (280g of wholemeal and 220g white)
300ml of water
A splodge of fermenter yeast. You can substitute this with any yeast, but it won't have a nutty beer flavour.
Step 1: Rack your beer, harvest the sludge
After you've brewed your beer, rack into bottles or a keg.
This brew was a robust London Porter (6.0%) and very dark.
The end result of the drained fermenter is the yeast trub at the bottom. It looks a bit like a planet to me...
Some people wash this and extract the live yeast with glycerol. No idea how they do this. I just tip the yeast cake into a bowl.
Step 2: Mixing the sponge
Mix half the bread flour (250g) with all the water and a splodge of yeast from the fermenter in a bowl. Mix, cover with oiled cling film and stick in a warm place for 12 hours.
Step 3: Mix and knead
I leave the sponge overnight. You'll understand why its called a sponge when it comes out. Its very full of air.
I got the idea for this step from the sourdough starter I used to make (I still have some frozen). The yeast cake from the fermenter has a lot of dead yeast and other bits in it (I understand that if you heat this with salt, the cells rupture and it makes marmite) and isn't very active. But letting it sit overnight means it gets a head start and it develops a much stronger and complex flavour.
In the morning add the rest of the flour, salt, oil and mix.
Knead for about 10 minutes. Then leave for an hour or two until its doubled in size.
Step 4: Doubling in size
You can see the difference in size here after an hour and a half.