In a large bowl add bread flour, whole wheat flour, rye flour and spelt flour and water (400g) and set aside for autolyze for 1 hour.

After an hour add sourdough starter and mix everything and set aside for 30 minutes.

Then add salt and rest of the water and combine everything and set aside for 1 hour.

When one hour is finished do a stretch and fold, set aside again for 1 hour and do second stretch and fold. Repeat this process after an hour too. Total you need 3 stretch and fold.

Then shape the dough and refrigerate overnight.

When you are ready to bake preheat oven to 475°F.

Remove the dough from the proofing basket and score , top with oats if you want. Then transfer to Dutch oven and close the lid and immediately place the top back on and return to the oven.

Turn the heat down to 450°F and cook for 15 minutes. After 15 minutes reduce the temperature to 425 F and bake for another 15 min. then remove the top of the Dutch oven and rotate the pan. Continue to bake the bread for another 10-15 minutes, until the crust is deeply caramelized. The internal dough temperature should register 205- 210 F.

If you want crackling crust after switching off the oven keep oven door ajar and keep the bread inside for 30 minutes. Once bread comes out of oven cool completely in the wire rack and cut it into slices and enjoy with some butter.