Once the yeast mixture is foamy, mix in the egg.

In a separate large bowl, combine bread flour, sugar, and salt.

Add the yeast mixture to dry mixture and mix well with a wooden spoon. Let it sit fo 15 minutes.

Knead in room temperature butter to the dough.

Let it rise for 1-2 hours or until the dough had doubled in size.

Deflate the dough and knead once more. Let it rise for another 1-2 hours or until the dough had doubled in size.

Deflate the dough and divide into equal size pieces. Shape each into a ball. Let it rise for 15 mintues.

Make each dough ball into a doughnut shape. Cover the dough with plastic wrap and dish towel and let it proof until doubled in size.

Uncover and let the surface of the doughnut dry for about 10 minutes. This prevents the doughnut from soaking up too much oil.

Heat the vegetable oil to 320 to 340°F. Fry the doughnuts for 3-4 minutes.

Once the doughnut cools down, coat with sugar.