Pour the lukewarm water into a mixing bowl or bread machine, then sprinkle the yeast over the top. Let it sit for 5 minutes to activate.

Add the remaining dough ingredients and mix by hand, with a stand mixer, or in a bread machine. Knead until the dough is soft and smooth.

Cover the bowl and let the dough rise in a warm place for 1 to 2 hours or until it has nearly doubled in volume.

Gently press down on the dough to release air, then divide it into 8 equal portions. Shape each into a smooth ball and flatten slightly to about 3 inches in diameter. Arrange on a parchment-lined baking sheet, cover loosely, and allow to rise for approximately an hour until they appear noticeably puffy.

For a softer crust, brush the buns with melted butter before the final proofing. Cover with cling film and let them continue rising for another hour. The buns are ready to bake when a light press leaves an indent that slowly springs back. If the dough rebounds too quickly, let it rise longer. If the indent remains, they may be over-proofed.

If a firmer, crispier top is desired, whisk the egg white with a tablespoon of water and brush the surface of each bun before sprinkling with sesame seeds.

Preheat the oven to 190°C (375°F). Bake the buns for 18 to 20 minutes, or until the tops are firm and set.

Remove from the oven and immediately brush with melted butter for a rich, glossy finish.

Transfer to a wire rack and allow to cool completely before serving.

Pour 180 g of tap water into the Thermomix bowl, then add 2 teaspoons of yeast, ensuring it lands in the water rather than on the blades.

Set the Thermomix to 37°C for 3 minutes at speed 1, then let the mixture rest for 5 minutes to allow the yeast to activate.

Add all remaining dough ingredients to the Thermomix bowl. To prevent mess, place the charcoal powder in first before turning on the machine. Mix on speed 5 for 15 seconds, then knead for 3 minutes on interval speed (wheat symbol).

Keep the dough in the Thermomix bowl with the measuring cup in place and allow it to rise until doubled in size, about 1 hour.

Remove the dough and divide it into 8 or 9 portions, depending on the desired size (approximately 95 g per bun for 8 buns). Shape into smooth rounds and lightly flatten each bun by pressing with your palm.

Brush with melted butter if a softer crust is preferred. Cover with cling film and allow the buns to rise for another hour. In warm climates, start checking after 30 minutes.

For a crispier exterior, whisk the egg white with 1 tablespoon of water and brush the tops before sprinkling with sesame seeds.

Preheat the oven to 190°C (375°F) and bake for 18 to 20 minutes, or until the buns are set.

Remove from the oven and brush with melted butter for a satiny, rich crust.

Cool on a wire rack before serving.