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, egg yolks, honey, oil and salt, mixing on low to combine. Replace the paddle for the dough hook.
Add flour, cassava flour, and xantham gum, 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.
Punch down dough to remove any air bubbles, and transfer to a floured surface.
Cut into the number of strands you’d like your braid to be, roll into ropes, and braid.
Make the egg wash: whisk together egg and water. Brush with egg wash, and top with sesame seeds (optional)
Bake for 40 minutes, turning the tray halfway through and brushing with additional egg wash.