In the bowl of an electric mixer, combine the yeast and 75ml warm water and stir by hand until the yeast has dissolved. Add the flour, sugar, eggs, orange zest and a pinch of salt and knead with a dough hook on low speed for about 8 min, until the dough is smooth and elastic.
Add the butter, a knob at a time, mixing well between each addition. Once all the butter has been completely incorporated into the dough, transfer the mixture to a lightly floured bowl and cover with cling film. Dough will still be quite sticky and wet. Set aside in a warm place until the dough has doubled in size – this should take at least an hour. Knock back the dough with your hand, then cover again with cling film and refrigerate overnight.
Flour your hands and divide the dough into 40 – 50 g balls (about the size of a golf ball) and place on a lined tray, leaving at least 5 cm between each one. Cover with a tea towel and set aside until the balls have doubled in size (again, in a warm place and for at least an hour).
While the dough is proving, heat half the cream in a small saucepan over medium heat – do not let it boil. Place the chopped chocolate in a large mixing bowl and pour over the cream, stirring until the chocolate has completely melted. Add the remaining unheated cream and stir until completely combined. Cover and place in fridge for about 15 minutes, until completely cool, then whip to soft peaks using an electric mixer. Stir through the chestnut puree and 1 heaped spoonful of Gewürzhaus Chocolate Spice. Transfer to a piping bag and place in the fridge.
Once doughnuts have proved, heat canola oil in a large saucepan (not too full) or deep fryer to 180°C. Fry the doughnuts in batches until puffed, golden and cooked through – about 3 minutes. Drain on absorbent paper. Mix the remaining Gewürzhaus Chocolate Spice and the Gewürzhaus Vanilla Bean Sugar together and transfer to a bowl. Use a chopstick or similar to poke a small hole into the side of the doughnuts, pipe as much filling as you can into each, without it overflowing and toss the doughnuts in the Gewürzhaus Chocolate Spice and Gewürzhaus Vanilla Bean Sugar mix .
These can be eaten immediately, or left to cool to room temperature, but best eaten the day of making.