Put water, yeast and sugar into a measuring cup or similar container, stir and set aside briefly.

Place the flour and salt in the bowl of your stand mixer and mix briefly. Add the yeast mixture and mix with the dough hook at low speed until the ingredients are combined. Next, add the butter and egg and let the dough knead in the machine for 10 minutes, until it is nice and soft and elastic.

Lightly oil a large bowl and your hands. Place the dough in the bowl and perform a series of stretch and folds: Gently lift one side of the dough and pull it upwards until it stretches but doesn't tear. Fold the stretched side over the center, rotate the bowl 90 degrees, and repeat this process three more times until all four sides have been stretched and folded, resulting in a smooth ball of dough.

Cover the bowl with cling film and let the dough rise for 1 to 2 hours, or until it has doubled in volume.

Press the dough down, place it on a floured work surface, shape it into a ball, and divide it into 6 equal pieces (approximately 140 grams each). Shape each piece into a round ball. Take one ball at a time and stretch it into a triangle about 15 centimeters long. Fold the top edges in slightly and then roll the triangle up towards the point, creating a roll 15 to 17 centimeters long.

Place the mini baguettes side by side on a baguette tray (alternatively, use a baking tray lined with baking paper) and let them rise again (now uncovered) for 45 minutes, until the baguettes have roughly doubled in volume.

After about 30 minutes, preheat the oven to 220°C / 430°F (top/bottom heat) and place a casserole dish with some water in the lower third.

Once the oven is fully preheated, score the surface of the baguettes with a knife at a 45° angle, then lightly spray (or brush) the rolls with water and place the baking sheet in the upper third of the oven. Bake the banh mi baguettes for a total of 20 minutes, removing the baking dish of water from the oven after 10 minutes.

Remove the rolls from the oven and let them cool. Then serve immediately (see notes) or let them cool completely and freeze in a suitable freezer bag for up to 3 months.