Combine yeast, sugar, and ½ cup water in a bowl of a stand mixer. Let sit for 5-10 minutes, or until the yeast starts to foam or “bloom”. **if the yeast does not bloom, you may need to get fresher yeast**
Add remaining water, egg yolks, honey, oil and salt, mixing on low to combine. Replace the paddle for the dough hook.
Add flour, one cup at a time, mix on low using the dough hook. Knead the dough until smooth and no longer sticky, adding more flour as needed. Transfer to a clean, oiled bowl. Cover with a clean, damp towel, and let rise until doubled in size, about 1 hour.
Preheat the oven to 350F. Line a baking tray with parchment paper, or grease a 9-inch cast iron pan.
Punch down dough to remove any air bubbles, and transfer to a floured surface.
Cut into 6 even pieces. Roll each piece into a rope, approximately 12 inches long. Cover with a damp cloth and let rest for 10-15 minutes.
Meanwhile, make the filling: combine the butter, sugar, tahini and cinnamon.
Flatten the dough strands with your fingers, place a line of filling in the center, and pinch to seal. Braid the ropes into 2 braids of 3 strands each. Coil into a circle, and pinch together.
Make the egg wash: whisk the egg white, and brush on the loaf. Top with coarse sugar.
Bake in a cast iron pan or baking tray for 40 minutes, turning the tray halfway through and brushing with additional egg wash.
Serve with optional cream cheese frosting.
Note: make the second half of dough into regular braid if you don't have two skillets