Mix the yeast into the room temperature milk. Set aside while you assemble the rest of the ingredients.
Place all of the dry ingredients into the bowl of a stand mixer fitted with the dough hook. Mix briefly to combine.
Cut the cold butter into 1/2inch cubes, and add them to the dry ingredients. Work the mixture on a low speed for about 2 minutes, or until the butter is mostly incorporated into the flour, with some larger flakes of butter still visible. Mix more than you would for traditional biscuits or a pie dough: Most of the butter should be incorporated into the flour.
Add the milk and yeast to the mixer, and mix on a medium speed, just until the mixture starts to cohere and there is no dry flour in the bottom of the bowl.
Dump the mixture out onto a floured surface, and pat and knead it together until it forms a smooth ball. Roll the dough out to about 1/2inch thickness, and use a doughnut cutter, a knife or a cookie cutter, to cut out as many donuts as you can.
Re-roll the scraps
Set aside your donuts in a cool spot for 30 minutes. (you do not want to put this in a warm spot that would cause the butter in the biscuits to melt and would make these a mess to work with.)
When the donuts have rested, heat about 2 inches of oil in a wide, deep pan, and bring it up to 350° F
Place a few donuts at a time into the hot oil (fewer is best you don't want the oil to bubble over and you want even browning). They need about 1 1/2 minutes per side.
When they have turned a dark golden brown and have puffed up to about twice their size,remove from the oil and drain on a wire rack with paper toweling beneath.
Toss the donuts in cinnamon sugar or powdered sugar, or glaze them.