Cream together the butter and sugar.
Then, add in the egg yolks a whip for about 5 minutes, till it’s light yellow and fluffy.
Next, add in the sour cream and whip for a further 5 minutes, this time, the mixture should be even paler and almost doubled in size.
Now, fold in the spices, coffee, vanilla, chocolate and salt. Being careful not to over mix and put this mixture to the side.
For the dry ingredients, sift together the plain flour, cornflour, cocoa powder and baking powder twice (It’s really important to double sift these together.)
Now, add in a cup of your flour mixture at a time, into the wet mixture, fold well each time, until all of the flour is gone and you are left with a sticky dough. (Make sure not to over mix at this stage, just fold the dry mixture enough so that it is combined.)
The dough is now ready and should be slightly sticky, bring the dough together so that it is one big ball (You don’t need to knead it) and place into a bowl, covered in cling film / saran wrap and allow it to rest in the fridge for at least an hour.
Once the dough has fully chilled, roll out the dough, on a floured surface, ½ to a ¼ of an inch in thickness, cut out the donuts and refrigerate for 30 minutes. You can also roll up the scraps, refrigerate them for around 15 minutes and re-roll and cut out more donuts (make sure to not roll out the dough too thin!)
Make the vanilla glaze by combining, icing sugar, vanilla, golden syrup / corn syrup and milk until you have a thin glaze that is solid in colour. It should be a light beige, almost white colour and be able to coat the back of a spoon, set this to the side.
Fill a heavy bottomed pan with 2L of oil and heat to 325°F.
In the meantime, set up a cooling rack with either parchment paper or paper towels underneath, to take the donuts out onto. Next to that, place a plate with a couple of chopsticks or skewers and a slotted spoon, now you're ready to fry. (more details here)
Carefully slide in the donuts one at a time, careful not to overcrowd the pan, or they won’t fry properly. Frying only 3 - 4 at a time.
Fry for 1 1/2 - 2 minutes on either side, they should be very lightly coloured on the outside and crackly on the top. Once fried, place them onto a cooling rack.
Once the donuts are cool enough to handle, immerse them into the glaze and place on a cooling rack, (with some parchment paper underneath to catch any extra glaze) and the donuts are ready!