Day 1 - Evening: Mix the Stiff Sweet Starter. Dissolve the sugar in water, add the starter, and mix well. Add the flour and mix until combined. Place in a clean container and ferment overnight.
Day 2: Set up the Proofer to 78°F (25°C). Mix the dough by adding water and stiff sweet starter to a bowl, breaking up the starter. Add the whole egg, yolk, sugar, honey, and oil. Stir to combine, then add flours and salt. Mix on low speed for 8 minutes until smooth.
Bulk ferment the dough for about 6 hours until it doubles in size. Chill overnight.
Day 3: Divide the dough into six pieces, shape into cylinders, and rest for 10 minutes. Roll each piece into a 15-inch rope.
Braid the Challah using the six strands. Pinch the ends together.
Final Proof: Proof for 4-5 hours at 78°F (25°C). Preheat the oven to 350°F (177°C) during the last 30 minutes.
Bake for 28-30 minutes until golden brown and a thermometer reads 190°F (88°C). Cool on a rack.
