Activate the yeast by sprinkling it over warm milk and letting it sit for about 5 minutes until frothy.
In a mixing bowl, whisk together flour and sugar. Add melted butter and the activated yeast mixture. Stir to combine.
Knead the dough on a floured surface for about 10 minutes until smooth and elastic.
Place dough in an oiled bowl, cover with a damp cloth, and let rise in a warm area for about 1 hour until doubled in size.
Punch down the dough, roll it out about half an inch thick, and cut out circles.
Heat vegetable oil in a deep pot to around 350°F (175°C). Fry each donut for about 2 minutes per side until golden brown.
Drain on paper towels before filling with pastry cream or jam.
