In a large mixing bowl, dissolve sugar in warm water. Sprinkle yeast over the top, and let it sit for about 10 minutes until foamy.
Mix in the butter, salt, and 2 cups of flour. Stir in the remaining flour, ½ cup at a time, until the dough pulls away from the sides of the bowl.
Turn the dough out onto a lightly floured surface, and knead until smooth and elastic, about 8 minutes.
Place the dough in a lightly oiled bowl, and turn to coat. Cover with a damp cloth, and let rise in a warm place until doubled in volume, about 1 hour.
Deflate the dough, and turn it out onto a lightly floured surface. Divide the dough into 8 equal pieces, and form into balls. Place on a greased baking sheet, and flatten slightly. Cover the buns with a damp cloth, and let rise until doubled in volume, about 40 minutes.
Preheat oven to 375°F (190°C). Bake in preheated oven for 12 to 15 minutes, or until golden brown.