Mix together ripe/active sourdough starter with all-purpose or bread flour and water. Cover loosely and let sit 3-4 hours at 78-80°F until doubled, bubbly & peaked.

About 30 minutes to an hour before the levain is ripe and active, mix together the oats and the very hot/boiling water. Stir together and set aside to thicken and cool.

To a large bowl, mix together ripe levain, oatmeal porridge, water and honey until incorporated. Add the salt, bread flour and whole wheat flour and mix together with a dough whisk until a wet and sticky dough forms.

Cover and let rest for 30 minutes.

Perform a series of 'stretch and folds' over the next 1 ½ hours.

Cover the dough and let rise for 1.5-2 more hours.

Tip the bowl upside down, allowing the dough to fall onto a clean counter surface. Wet your hands and the bench knife if needed and push the bench knife under the dough on one side and your free hand on the other side to tuck the dough under itself.

Let the dough rest uncovered for about 30 minutes at room temperature.

Prepare a shallow bowl with oats for the topping. Line a bowl or banneton with a kitchen towel or hair net in the bowl and liberally flour as needed.

Cover the dough with the tea towel/shower cap/plastic wrap and refrigerate overnight or up to 14-20 hours.

Put a Dutch oven (top and all) into the oven and preheat to 500°F for 30 minutes.

Use a very sharp knife or bread lame to score the dough.

Carefully remove the Dutch oven from the 500°F oven. Take the lid off and place your bread into the Dutch oven. Lower the temperature to 450°F and bake for 25 minutes. After 25 minutes, take the lid off the Dutch oven and continue baking for 20 minutes until the bread is a crackly deep brown.