In a mixing bowl, combine flour, yeast, sugar, and salt. Mix well.

Add warm milk and eggs, and mix until a dough forms.

Knead in softened butter until smooth and elastic.

Cover and let rise in a warm place for about 1 hour or until doubled in size.

In a saucepan, combine corn, heavy cream, sugar, and salt. Cook over medium heat until warm.

In a small bowl, mix cornstarch with a little water to create a slurry.

Add the slurry to the warm corn mixture and stir until thickened. Remove from heat and stir in vanilla extract.

Let cool completely before using.

Once the dough has risen, punch it down and roll it out to about 1/2 inch thickness.

Cut out donuts using a donut cutter or two round cutters.

Let the cut donuts rise for another 30 minutes.

Heat vegetable oil in a frying pan to 350°F (175°C).

Fry donuts until golden brown on both sides, about 2-3 minutes per side. Drain on paper towels.

Using a pastry bag, fill each donut with the corn custard filling.

Mix powdered sugar with milk to create a glaze. Dip the tops of the donuts in the glaze.

Let the glaze set before serving.