In a bowl, mix together the dough ingredients. Once you have a rough dough tip out onto a work surface and knead for 10 minutes, trying to avoid adding any more flour. It will seem sticky to begin with but will tighten up and become more elastic the more you knead it.
Once smooth return to the bowl and cover with cling film. Allow to double in size for at least 1 hour.
Once proved, tip the dough back on to the work surface and knead a little more. Divide the dough into 12 equal pieces (I use my scales for this).
Roll each piece into a round making sure you pinch the seam well so it has a smooth exterior. Place on a lightly flour baking tray and cover loosely with cling film. Leave for 30 minutes.
In the meantime, half fill a large saucepan with sunflower oil and heat to 180°C. Use a sugar thermometer to keep the temperature consistent. Weigh out all 150g sugar in a shallow bowl.
Fry the doughnuts two or three at a time making sure you don’t overcrowd the pan. They will need 8 minutes in the pan - make sure to cook them evenly on each side and cooked through fully. If they colour too quickly turn the heat down.
Once done, remove from the oil with a slotted spoon and immediately add to the sugar bowl. Cover fully, then shake off any excess. Set aside. Cook the remaining doughnuts and roll in sugar as before. Allow the doughnuts to cool completely.
Before serving use the handle of a teaspoon to make a hole in the doughnuts. Inserting it half way and twisting it to make a hole. Transfer the custard into a piping bag and fill the doughnuts via the hole you have created. Allow a little to over flow in the top.
Repeat with the others before chopping the honeycomb into pieces and using them to decorate the tops. Serve immediately or store in an airtight container for up to 2 days.