In a small bowl, combine the warm milk and sugar. Sprinkle the yeast over the milk and let it sit for about 5-10 minutes until frothy.
In a large mixing bowl, combine the all-purpose flour and salt. Make a well in the center and add the yeast mixture, melted butter, and egg.
Mix until a dough forms, then knead on a floured surface for about 10 minutes until the dough is smooth and elastic.
Place the dough in a lightly oiled bowl, cover it with a clean cloth, and let it rise in a warm place for about 1-1.5 hours, or until it doubles in size.
Punch down the risen dough and divide it into equal portions (about 12 pieces).
Flatten each piece of dough into a small disc and place a spoonful of fruit jam or sweetened poppy seed filling in the center.
Gather the edges of the dough and pinch them together to seal the filling inside. Shape each filled dough piece into a smooth ball.
Prepare a steamer or a large pot with a steamer insert. Bring water to a boil.
Lightly brush the steamer insert with oil or melted butter to prevent sticking.
Place the filled dough balls in the steamer, leaving some space between them to allow for expansion.
Cover and steam for about 15-20 minutes, or until the buchty are puffed and cooked through.
Carefully remove the steamed buchty from the steamer.
Drizzle them with melted butter and dust with powdered sugar.
Enjoy your meal!