In a large mixing bowl, combine flour, sugar, yeast, and salt. In a separate bowl, warm milk, whisk in eggs and melted butter, and add to dry ingredients.

Shape the dough into a ball, place in a greased bowl, cover, and let rise for 1 to 2 hours until doubled in size.

Punch down the dough, roll out to ½ inch thickness, cut into rounds, arrange on a floured sheet, cover, and let rise for 30 to 45 minutes.

Heat oil to 350°F, fry dough rounds until golden brown, about 2 to 3 minutes per side, then transfer to a wire rack.

Allow to cool slightly, then fill doughnuts with pastry cream using a piping bag, and dust with powdered sugar before serving.