Check the instructions on your yeast packet. Some yeast can be added straight to the dry ingredients while others need to be activated in lukewarm liquid first. If so, activate it in a bit of lukewarm milk, avoiding adding extra liquid.

In the mixer bowl, combine the flour, sugar, and yeast by stirring.

Evenly distribute cubes of butter over the flour, then add the eggs, lukewarm milk, vanilla, and salt. Attach the dough hook to the mixer and knead at low speed for 10 minutes.

After 10 minutes, the dough should be smooth, elastic, and slightly tacky. Transfer to a cleaned surface, knead 2-3 times into a smooth ball, and let rise covered for 2-3 hours until tripled in size.

Once risen, flatten the dough and roll into a rectangle about ½ inch thick. Cut out round doughnuts about 3.5 inches in diameter.

Set the cut doughnuts on a lined surface, cover loosely, and allow to prove for 1-1.5 hours until tripled.

Heat oil in a deep pan until it reaches 170°C/337°F.

Fry the doughnuts for 2 minutes on each side, then drain on kitchen paper and roll in sugar.

Fill each doughnut with prepared pastry cream using a piping bag.

Serve immediately or store in plastic containers for 1-2 days.