01 - In a large bowl, combine flour, sugar, salt, and instant yeast until well blended.
02 - Add warm milk, softened butter, and egg to the dry ingredients. Mix until a soft, sticky dough forms.
03 - Knead the dough by hand or with a stand mixer for 8–10 minutes until smooth, elastic, and no longer sticky.
04 - Place the dough in a greased bowl, cover with plastic wrap or a damp towel, and let rise in a warm place for 1 hour until doubled in size.
05 - Punch down the risen dough and divide into 8 equal pieces. Shape each piece into a smooth ball and place on a parchment-lined baking sheet.
06 - Cover the shaped dough and let rest for 30 minutes until slightly puffed.
07 - Heat vegetable oil in a deep pot to 340°F, using a kitchen thermometer to maintain temperature.
08 - Fry the donuts in batches of 2–3, turning occasionally, until golden brown on both sides, about 2–3 minutes per side.
09 - Remove with a slotted spoon and drain on paper towels. Allow to cool completely before filling.
10 - Whip cold heavy cream to soft peaks. Add sweetened condensed milk, powdered milk, and vanilla extract. Continue whipping until stiff peaks form.
11 - Transfer the cream to a piping bag fitted with a round tip. Make a small incision in the side of each cooled donut and pipe in the filling generously.
12 - Roll filled donuts in powdered sugar until thoroughly coated. Serve immediately for the best texture and flavor.