In a small bowl, dissolve the yeast in the milk and add the sugar. In another bowl, sift the flour and salt together and add the cooled melted butter.
Add the yeast mixture to the flour mixture, and turn out onto a floured counter and knead until the dough is smooth and elastic. Place the dough in an oiled bowl, cover with a clean towel and let rise in a warm, draft free place to 45 minutes.
Turn dough out onto the freshly floured board and shape into 9 balls. Place dough balls into a buttered and floured 9 inch square pan. Let them sit, covered for another 15 minutes to rise again. Preheat the oven to 425° F (220 C).
Bake for 15-20 minutes until browned and puffed. Split open and serve warm.