Place cereal mix in a large bowl or bowl of stand mixer. Pour boiling water on top.
Let the mixture cool for about an hour until it reaches room temperature. Make sure it isn’t too hot, so it doesn’t kill the yeast in your starter!
Add the rest if the ingredients to the mixer and knead with the dough hook on medium speed until the dough comes together, pulls away from the sides of the bowl, and passes the window pane test. This can take a very long time, sometimes up to 20 minutes. Knead it until it is a smooth and glossy dough. Base the time on how the dough feels.
Cover with a damp towel, lid, or plastic wrap and proceed to the next step.
Bulk ferment until doubled. The bulk fermentation time may take anywhere from 4-8 hours depending on the temperature in your house.
Butter or line with a piece of parchment paper a 9×5 inch loaf pan.
Shape by rolling the dough flat into a rectangle and rolling it up.
Add to parchment lined or buttered loaf pans.
Cover with a towel or plastic wrap for 2-4 hours at room temperature, or until doubled.
When the dough is about ready to bake, preheat the oven to 375 degrees.
Optional: Crack an egg into a small bowl and whisk together. Using a pastry brush, brush the top of the dough with the egg wash and sprinkle with a small amount of oats if desired.
Bake for 45 minutes, or until golden brown on top.
Allow to cool completely before slicing.