In a bowl, blend the lukewarm milk with instant yeast. Let this sit for a few minutes until frothy, which activates the yeast for that perfect rise.

Add the white caster sugar, vanilla sugar, vanilla cream, and softened butter to the yeast mixture. Stir well until fully combined, creating a rich and decadent base for your donuts.

Gradually add in the flour, baking powder, and salt to the wet mixture. Mix until a soft dough forms, ensuring all ingredients are well integrated for the best texture.

Turn the dough out onto a floured surface and knead until smooth and elastic, about 5 minutes. Place it in a greased bowl, cover with a cloth, and let rise until it doubles in size—roughly 1 hour.

Roll out the risen dough to about 1/2 inch thick, then cut into donut shapes using a cutter. Place them on a baking sheet and let them rise again for about 30 minutes.

Heat oil in a deep fryer to 350°F. Fry the donuts in batches until they are golden brown on both sides, approximately 2-3 minutes per side.

Remove the donuts from the oil and allow them to drain on paper towels. While still warm, generously coat them in extra granulated sugar for that delightful crunch.