• Mix the yeast and sugar into the lukewarm milk and leave for 10 minutes until it starts to bubble. This tells you your yeast is active and ready to work.
  180 ml milk, 2 teaspoon instant yeast , 50 gr sugar
• Add the flour, butter, vanilla sugar and salt to a large bowl. Pour over the yeast mixture and knead with a stand or hand mixer. Add the egg yolks one by one and continue kneading for 5 minutes until you have a smooth, elastic dough. Place in a lightly greased bowl, cover with a kitchen towel and leave to rise for 60 minutes.
  500 gr all-purpose , 60 gr butter , 1 teaspoon vanilla extract, ½ teaspoon salt , 3 egg yolks
• Turn the risen dough out onto a lightly floured surface and knead briefly by hand. Divide into 12 equal pieces (approximately 60g / 2oz each). Using a circular motion with the palm of your hand, gently roll each piece on the floured surface to create a smooth ball shape.

  Alternatively, roll the dough between the palms of both hands using the same circular motion. Don't worry if they look small - the dough balls will enlarge during the final rise. Place on a lined baking tray, cover with a tea towel and leave to rise for a further 30 minutes.
• Place the balls on a lined baking tray and cover with a tea towel. Leave to rise for a further 30 minutes. 
• Pour the oil into a large pot and heat to 170°C (338°F). If you don't have a thermometer, dip a wooden spoon into the oil - it's ready when gentle bubbles form around it. It is important not to fry at too high a temperature, otherwise the outside will cook before the inside is done. F
  750 ml neutral oil
• Fry each Berliner for approximately 3 minutes on each side until golden brown. Remove with a slotted spoon, pat dry on a kitchen towel to absorb any excess oil and leave to cool for at least 20 minutes before filling.
• Remove them with a slotted spoon and pat them dry on a kitchen towel to absorb the remaining grease. Leave to cool down for at least 20 minutes before filling. 

Filling the donut

• Fill a piping bag fitted with a long, narrow nozzle (¼ inch / 7mm) with your chosen filling. If your jam contains bits or seeds, strain it through a sieve first to prevent the nozzle from blocking. Optionally, warm the jam slightly beforehand to help it flow more easily through the nozzle. Insert the nozzle into the side of each cooled Berliner and squeeze gently until you can feel the donut getting heavier.
  250 g jam
• Dust generously with powdered sugar and serve immediately.