Prepare the preferment and the soaker and allow it to mingle for about 8-12 hours at room temperature. This could be done either very early in the morning or overnight depending on your style. Once properly mingled, mix the final dough, add the soaker, and start to knead.

Add the preferment in chunks. If you are kneading by hand, give it about 8-10 minutes of kneading. If you are mixing by mixer, 1-2 minutes on low speed and 2-3 minutes on second speed. This is a sticky dough, due to the increased hydration. Try to avoid adding extra flour if possible.

During the bulk fermentation, give the dough two to three folds depending on your gluten structure, 25 minutes apart.

Then divide the dough into two equal-sized portions and pre-shaped into rounds. 15 minutes later form the dough into two tight boules, place in a dusted brotform and proof for 70 minutes.

After proofing, the boules should be heavily brushed with mustard and topped with sunflower seeds.

Bake the loaves in a preheated oven at 450 degrees, 15 minutes with steam (or in Dutch ovens), and then vent the steam and reduce the oven temperature to 400 degrees. Bake for an additional 25 minutes.

Cool completely before slicing and serving.