3 cups (405 grams) bread flour
1 1/2 tsp (8 grams) salt
1/4 tsp instant dry yeast (if fermenting for 18 hours), or 3/4 tsp instant dry yeast (if fermenting for 6 hours)
1 1/2 cup + 2 tbsp (385 grams) plain unsweetened yogurt containing active cultures
1/3 cup sunflower seeds, optional
1/3 cup flax seeds, optional
Instructions
In a stand-mixer with dough-hook, or in a large bowl by hands, mix bread flour, instant dry yeast, salt and plain yogurt, plus seeds if using, on medium-low speed for 2 min until a dough forms. If the dough is too dry and has difficulty coming together, add 1 tbsp more plain yogurt. If you'd like, continue to knead the dough on medium-low speed, or with your hands, for a few more minutes until springy. The dough should be very sticky, but able to retain shapes.
Cover the bowl with plastic wrap and let ferment at room-temperature for 18 hours (NO MORE than 20 hours or the yogurt may spoil and become bitter!), or 6 hours depending on your schedule (note that the amount of yeast varies). The dough should almost doubled when finished.
After fermentation, dust the counter with flour then transfer the dough on top. Use just enough flour to prevent the dough from sticking, fold the dough gently (without crushing all the air bubbles inside) over itself like folding a letter. Turn 90 degrees and fold again. Then shape the dough into a ball-shape. Transfer to a piece of floured parchment paper, then cover a large bowl on top and let proof again for 1 ~ 2 hours. The dough is ready when it almost double in size again, and should not spring back when you press it with a finger.
45 minutes before the dough's ready, preheat the oven on 450F/225C with a large dutch oven, or a heavy-bottom pot (both should come with lid) inside. To bake the bread, lift the parchment paper to transfer the dough into the preheated pot, cover the lid and bake for 30 min. Then remove the lid, and bake until the crust is golden browned.
Let cool on a rack for 20 min.