In a mixing bowl, combine warm water, sugar, and yeast. Let it sit for about 5-10 minutes until frothy.

Add melted butter, salt, and 2 cups of flour to the yeast mixture. Stir until combined, then gradually add the remaining flour until a soft dough forms.

Transfer the dough to a floured surface and knead for about 5-7 minutes until smooth and elastic.

Place the dough in a lightly greased bowl, cover it with a kitchen towel, and let it rise in a warm place for about 1 hour, or until doubled in size.

Punch down the risen dough and turn it out onto a floured surface. Divide it into 12 equal pieces and shape each piece into a smooth ball.

Arrange the dough balls on a baking sheet lined with parchment paper. Cover them again and let them rise for about 30 minutes until puffy.

Preheat your oven to 375°F (190°C) while the buns complete their second rise.

If using, brush the tops of the buns with the egg wash for a golden finish. Bake for 20-25 minutes until golden brown and hollow when tapped.