Add the active sourdough starter, water, and flour to a bowl. Mix until combined, cover, and rest in a warm spot for four hours or until the levain has doubled in size.

In the bowl of your stand mixer, combine water, levain, eggs, and honey. Add flour to the bowl, turn the mixer on, and mix for about 2 minutes until the dough comes together.

Cover the bowl and autolyse/rest for 30 minutes.

Turn the mixer on again and add the salt and ¼ of the oil. Knead for 2 minutes or until the oil is thoroughly mixed in. Repeat until all the oil has been added.

Knead for 5-10 minutes on low-medium until the dough passes the windowpane test.

Oil a large baking bowl. Transfer the dough to the bowl, and lightly oil the top of the dough as well. Cover the bowl and rise for five hours at around 75°F/24°C.

Transfer the dough to the fridge and cold-proof for 10-15 hours or overnight.

Dump the dough onto a work surface. Divide the dough into 6 equal pieces. Roll each piece into seamless rounds and cover with an oiled piece of plastic wrap to rest for 10 minutes.

Roll each round into rectangles about 8 in/20 cm long and roll it up like a roulade. Cover the roulades and rest for another 10 minutes.

Use your hands to roll and extend the roulades into 40-45 cm strands. Braid the challah loosely to allow for expansion during the final proof.

Transfer your challah to a lined baking tray. Loosely cover the tray with plastic wrap and place the tray in a warm spot around 78°F/26°C. Proof for 4-6 hours.

Preheat your oven to 350°F/180°C.

Mix up your egg wash by whisking together egg and water. Gently brush your challah with egg wash and sprinkle sesame seeds on top.

Bake for 25-35 minutes, until golden. Cover with foil if it browns too quickly. Internal temperature should be at 95C/203F when it is done.

Transfer to a wire rack and cool completely before serving.