It is baking time – woohoo! But ok, a warning is needed now – you’ll only get this bread tomorrow. And another warning – there won’t be anything left of it after tomorrow.
But, today you’ll get to make the sponge and here is what one needs;
50g Strong white flour (I use 12% protein)
40g Water (cool)
1g Fresh yeast
So, doing a little math you can see this sponge is for example 80% hydration – the amount of water is only 80% of the amount of flour, so it will be a bit more dry mixture. And this now is a sponge, not a sourdough ‘since a sourdough never has any commercial yeast in it.
To begin with, make sure you first dissolve the yeast well into a needed amount of water. After that you can mix the flour in with a spatula, scrape the edges down and cling film/close the lid of the jar. You ought to leave it in a cool place for overnight, but fridge could already be a bit too cold. The required temperature depends alot on whether you’ll be baking in the morning or in the evening – the warmer the sponge spends the time in, the faster it becomes active and also the faster it starts loosing it’s bubbles. But I’m sure you’ll find a good place for it.