In a bowl of stand mixer, dilute starter with water, stir in sugar and add in bread flour. Mix with paddle attachment until well mixed and all come together. It can be done by hand mixing too.

Cover and let it ferment until tripled. I prepared a night before and leave it in aircond room (approximately 24 - 25C room temperature) overnight until tripled. It took about 8 - 9 hours depending on your starter. It should take around 4 - 6 hours to get triple at room temperature at 28C - 30C. The starter should look smooth and round dome. It shouldn't collapse.

Put all ingredients (except butter/olive oil), including all the stiff starter into a bowl of stand mixer. I usually torn the stiff starter dough slightly.

Slightly combine the mixture by hand with the paddle attachment before turning on the machine so that the flour will not splash out. Using the paddle attachment, mix at low speed (#2 for KA) until all incorporated. Maybe less than a minute. This step is critical to prevent an uneven mixed dough as the stiff starter is rather hard and a dough hook may not be able to mix it well enough.

Change to hook attachment and knead for another 3 minutes at low speed (#2 for KA) or until the dough comes together.

Add in oil and continue kneading at low speed (#2 for KA) for about 5 minutes.

I stopped after 5 minutes to scrape down the dough from the hook to be sure it is evenly kneaded and also to prevent the motor from overheating.

Continue kneading for another 4 minutes at low speed (#2 for KA).

Change to medium speed (#4 for KA) and continue kneading for a minute or until the dough become smooth and shining, and reach window pane stage.

In the same bowl, let the dough rest for 15 - 60 minutes. Keep it covered with clingfilm or use a lid. This dough I rested for 45 minutes and the dough rose slightly in 45 minutes. (I did not find any big differences between 15 minutes to 60 minutes rest. So, please follow your schedule).

Transfer the dough to a clean floured surface then divide dough into 6 equal portions. Please use a kitchen scale if you want to be exact.

Form each portion to a ball. Rest for 10 minutes.

Please watch the video "How To Shape & Score Banh Mi"

Place the bread dough onto the baguette tray.

Let the rolls proof at a warm place until the dough rise about double in size. This one took approximately 2 hours minutes at at room temperature of 29C. The duration of proofing depends on your ambient temperature and starter.

Preheat oven with baking stone and lava rocks at 200C (fan-forced) for 30 minutes before baking.

Once the oven is ready, score the dough (please watch the video). Wet the blade with water for easy scoring. Keep the blade at 45° angle, and slash across the dough lengthwise. I scored twice just to make sure it is deep enough.

Spray water on the bread and bake immediately.

Open the oven door, place the bread dough (with the baguette tray).

Pour one cup of hot water into the lava rocks.

Close the door immediately.

Reduce temperature to 190C (fan-forced) and bake for about 10 minutes.

Remove the lava rocks and continue baking for another 10 minutes or until golden brown. Rotate the bread if the oven heat is uneven and also flip the bread just to make sure the bottom is evenly baked too.

Once is ready, swift off the oven. Leave the bread inside the oven for about 10 minutes with door open.

Remove Banh Mi from oven and let them cool on rack.