Feed the sourdough starter approximately 12 hours before dough preparation. In a clean jar, combine flour, water, and unfed starter. Mix thoroughly, loosely cover, and allow it to ferment at room temperature until doubled in size and bubbly. This mix yields a little more than needed to account for any transfer loss.

To prepare the dough, combine flour, water, honey, salt, and the active sourdough starter in a large bowl. Stir with a spatula or by hand until all dry elements are incorporated. Cover and rest at room temperature for 30 minutes.

Perform three sets of stretch and folds at 30-minute intervals. Moisten your hand, lift one side of the dough, and fold it over itself. Rotate the bowl a quarter turn and repeat until a full rotation is complete, forming a taut dough ball. Cover after each round of folds. Alternatively, a stand mixer fitted with a dough hook can be used; knead on speed 3 for 8–10 minutes.

Cover and allow the dough to rise until doubled in volume, typically around 6 hours at 72°F (22°C). Once risen, refrigerate for up to 2 days if deferring baking. If baking the same day, proceed directly to shaping.

Transfer the dough onto a lightly floured surface and divide into six equal pieces (112–115 g each). Shape each portion into a round ball, flour the tops lightly, and place onto a parchment-lined baking sheet. Cover with a kitchen towel and allow to rise for 1–2 hours until visibly puffy.

Preheat the oven to 375°F (190°C). Whisk together the egg and water, then brush the tops of the buns. Add sesame seeds if desired. Bake for approximately 25 minutes or until golden brown. Allow to cool before slicing.