In a small bowl, combine the warm water, yeast, and sugar. Stir gently and let it sit for about 5-10 minutes until it becomes frothy.
In a large mixing bowl, combine the flour and salt. Make a well in the center and pour in the activated yeast mixture, butter, and egg. Mix until a shaggy dough forms.
Transfer the dough onto a lightly floured surface and knead for about 8-10 minutes until it becomes smooth and elastic.
Place the kneaded dough into a greased bowl, cover it, and let it rise in a warm environment for about 1 hour, or until doubled in size.
Once risen, punch down the dough to release the air. Divide it into equal portions (about 8-10 pieces). Shape each piece into a round ball and place them on a baking sheet lined with parchment paper.
Cover the shaped buns with a towel and let them rise again for about 30-45 minutes until they puff up.
While the buns are rising, preheat your oven to 375°F (190°C).
Brush the tops of the buns with the eggwash and sprinkle with sesame seeds if desired. Bake in the preheated oven for 15-20 minutes until golden brown.
Once baked, remove the buns from the oven and let them cool on a wire rack.
