Chill a large jug or bowl in the freezer for the panna cotta.
Heat double cream, vanilla, and sugar in a saucepan until just boiling.
Whisk in the soaked gelatine and buttermilk until well combined.
Sieve the mixture into the chilled jug and stir in the espresso.
Refrigerate the mixture and whisk every five minutes until it starts setting.
Pour into moulds and chill for at least two hours until completely set.
Mix flour, sugar, salt, and yeast in a mixer, then add warm milk and egg.
Knead the dough for five minutes until smooth and elastic.
Gradually knead in softened butter and then knead by hand on a floured surface.
Let dough rise in a warm place for two hours until doubled in size.
Form into small balls and let rise on a tray for 20 minutes.
Fry doughnuts in 190°C oil for 4 minutes until golden-brown and dust with sugar.
Melt chocolate in a bowl over simmering water.
Boil sugar with 100ml water and stir the syrup into the melted chocolate.
Unmould panna cotta and serve with doughnuts, sauce, nuts, and mint.