In a mixer, combine all dough ingredients and mix for about 12 minutes until smooth. Let it rise for an hour or until doubled in size.
For the cream, whisk egg yolks, cornflour, vanilla, and sugar. Boil milk and add it to the mixture, then cook while stirring until it thickens. Add butter and white chocolate, and stir until smooth. Chill the cream.
Divide the dough into 45-50g balls and let them rise again for about 1.5 hours.
Fry the doughnuts in oil heated to 160-170°C, about 3 minutes per side. Let them cool.
Fill the doughnuts with the chilled cream.
For the caramel, heat sugar and water in a pan until it forms a caramel. Dip the top of each doughnut in the caramel and let it cool.