Mix together 120 g water with the strong white flour and the semolina. Add a few grains of instant or dry yeast or a small crumb of fresh yeast. Knead well for 10 minutes and then cover with cling film and pop in the fridge for at least 24 hours. If you would like to, you can leave it in the fridge for up to 4 days. This will build flavour.
Day 2 (or whenever you are ready to bake)
If using instant or fresh yeast:
Remove the bowl from the fridge and add the spelt flour, the remaining water (300 g), the salt and the yeast. Knead well for 10 minutes and then pop back in the bowl. Cover and let rest for 2 hours at room temperature.
If using dry yeast:
Measure the spelt flour into a big mixing bowl. Make a well in it and sprinkle in the yeast. Pour on the remaining water (300g). Let it sit for 15 minutes. Then add the flour mixture from the bowl in the fridge and the salt and knead for 10 minutes. Pop back in the bowl, cover and let rest for 2 hours at room temperature.
Once the dough has rested, pull it out gently on to a non floured surface. Shape it into a tight sausage or a cob. Place it in a proofing basket, tin, or on a baking tray, cover and let it rest for 1 hour.
Preheat the oven to 230 degrees C.
Flour the top of the loaf and pop it in the oven. (If you are proofing it in a basket, roll it out of the basket and on to a prepared baking tray.)
Bake for 25 minutes and then tap the bottom of the loaf. If it sounds hollow it is done.
Let cool completely before you cut into it. YUM!