In a bowl, whisk the warm milk with sugar and instant yeast until combined. (Assumption: milk is warmed to about 100–110°F / 38–43°C.)
Whisk in the egg and salt until smooth.
Add the flour and mix until a shaggy dough forms.
Knead the dough until it starts to smooth out, then knead in the room-temperature butter until fully incorporated and the dough is soft and elastic.
Cover and let rise until doubled in size (about 60–90 minutes).
Roll dough to about 1/2-inch thickness and cut donut shapes.
Let cut donuts rise until puffy (about 20–30 minutes).
Fry in hot oil until golden on both sides (assumption: 350°F / 175°C, 1–2 minutes per side).
Drain briefly, then coat as desired
