Make the yeast mixture: In a large measuring cup, combine warm milk, yeast, and granulated sugar. Let froth for 5-10 minutes.

In a stand mixer, combine flour, sugar, salt, butter, egg, egg yolks, vanilla, and the frothy yeast mixture. Mix on low, then high speed for 10-15 minutes.

Place the dough in a greased bowl, cover, and let rise until doubled (1-2 hours).

Punch down the dough, roll out to 1/2 inch thick, and cut out circles. Let rise for 30 minutes.

Heat corn oil to 340°F. Fry each donut for 2 minutes per side until golden brown. Transfer to paper towels.

Once cooled, roll donuts in sugar.