This is how I made them;
2.5 teaspoon of yeast
1 cup milk
1/4 cup butter
2 cups flour
2 tablespoons sugar
Warm the milk up to 110F. Add the sugar and yeast and let proof for about 10 minutes. Stir in a whisked egg and the melted butter. Add the flour and stir until a dough forms. Knead until smooth and elastic. Cover with a clean towel and let sit in a warm place for an hour.
Roll the dough to 3/8" thick. Cut into rounds with a cookie cutter or a glass. Cut the holes out with a smaller round, like a spice bottle.
Heat oil up to about 380F. Fry until golden, flipping the donuts halfway through.
Drain and blot to remove excess oil. Dip in cinnamon sugar.