Combine the soaker ingredients in a bowl or measuring cup. Leave covered for at least an hour, as long as overnight.
Add wheat flour, bread flour, yeast, salt and brown sugar to a stand mixer. Stir on low to combine.
Next add honey, the soaker, water and buttermilk.
Mix the ingredients until they clear the sides of the bowl and form a sticky ball.
On a floured counter, knead the dough by hand for 10-12 minutes.
Place the dough into a lightly greased bowl. Cover and let rise until doubled, an hour to an hour and a half.
Deflate the dough and press into a rough rectangle, 6x8 inches.
Roll the dough tightly away from you, tucking the ends under as you go.
Pinch the seams together and place seam side down in a greased loaf pan.
Cover and let rise until the rough crests the lip of the pan, about another hour.
While the dough is rising, preheat the oven to 350 degrees.
Once risen, gently brush or spritz the top of the dough with water. Sprinkle with sesame seeds.
Bake for 40-45 minutes until golden, rotating halfway through.