In a large bowl, combine the softened butter with 1/3 cup of the sugar, the boiling water and the salt. Stir until the butter is melted. In a small bowl, combine the yeast with the warm water and the pinch of sugar. Let stand until foamy, about 5 minutes. Add the yeast to the butter-sugar mixture. Beat in the egg until smooth. Stir in the flour with a wooden spoon until a dough forms. Gather the dough into a ball in the center of the bowl, cover with plastic wrap and refrigerate overnight. Let the dough stand at room temperature for 2 hours. On a well-floured surface, roll out or pat the dough about 1/2 inch thick. Using a 2 3/4-inch round biscuit cutter, stamp out about 14 rounds, as close together as possible. Gather and re-roll the scraps to cut out 2 more rounds. Lightly butter an 8-by-11-inch glass baking dish. Fold the dough rounds in half and arrange the rolls in the prepared baking dish in 2 rows of 8. Brush the rolls with the melted butter and sprinkle with the sesame seeds. Let stand until slightly risen, about 30 minutes. Preheat the oven to 425°. Bake the rolls in the center of the oven for 20 minutes, or until risen and the tops and bottoms are golden. Turn the rolls out into a basket and serve piping hot.