Step 1

Place 1/3 cup warm water, 5 tablespoons olive oil, 3 tablespoons maple syrup, 2 teaspoons of the kosher salt, and 2 large eggs in a stand mixer and mix with a fork until combined. Add 3 1/2 cups bread flour and 1/3 cup sourdough starter. Knead with the dough hook on medium-low speed (setting until a shaggy dough forms, about 2 minutes.

Step 2

Scrape the dough onto a lightly floured surface. Knead by hand until the dough begins to smooth out and become tacky, 6 to 10 minutes. If the dough is too firm, add more water 1 tablespoon at a time until the dough kneads easily. If the dough is too wet, add more flour 1 tablespoon at a time.

Step 3

Lightly coat a large bowl with cooking spray. Add the dough and cover the bowl with plastic wrap. Let rise in a warm place (like the inside of a turned off microwave) until the dough has nearly doubled in size, 8 to 12 hours.

Step 4

Dump the dough onto a lightly floured work surface and knead until it comes together. Divide the dough into 6 portions. Roll each piece from the center outwards with your hands into a 16-inch long rope. Braid 3 ropes together, then braid remaining 3 ropes together. Twist the 2 braids together, then tuck the ends under the loaf.

Step 5

Line a baking sheet with parchment paper and place the loaf on top. Lightly coat a sheet of plastic wrap with cooking spray, then place over the loaf spray-side down. Let rise in a warm area until puffy and jiggly, 3 to 4 hours.

Step 6

Arrange a rack in the middle of the oven and heat the oven to 350℉. Meanwhile, place 1 large egg yolk, 1 tablespoon water, and the remaining 1/8 teaspoon kosher salt in a small bowl and whisk with a fork to combine. Brush the bread with the egg wash, then sprinkle with 1 to 2 tablespoons sesame seeds.

Step 7

Bake until the challah is golden brown, 35 to 45 minutes. If the challah is getting too dark, tent it with a sheet of aluminum foil. Transfer to a wire rack and let cool to room temperature before slicing.