Heston Blumenthal's unusual recipe makes beautifully light donuts with a crackly popping coating
Heston: "Donuts are normally made with flour but substituting some of the flour with potato flesh gives a lighter, springier donut which can then be coated in crystallised potato and dipped in potato milk jam. . . . all this from the humble spud! The coloured, exploding coating is really for the kids but I love it too!
For the potato sugar
To start the donuts, preheat the oven to 180ºC/fan 160°C/gas mark 4.
Prick the potatoes all over with a fork then coat them in groundnut oil and place them on a layer of salt spread on a baking tray. Place the tray in the preheated oven for 2 hours.
Remove the potatoes from the oven and cut them in half.
Place the smoking chips on the bottom of a saucepan and place over a high heat. Using a blow torch, light the chips until they begin to smoke.
Using aluminium foil, make a ‘pillow’ and place in the centre of the pan. Place the potatoes on top of the pillow and cover the pan with a lid. Allow to smoke for 5 minutes.
When smoked, scoop the flesh from the potatoes and reserve the skins. Put the potato flesh through a sieve and weigh out 130g. Reserve the remaining flesh for the potato sugar (you will need 70g to mix with the food colouring).
Place the smoked skins in a pan with the milk over a medium heat and bring to a simmer for 5 minutes. Remove from the heat and allow to infuse for 20 minutes before straining.
In a bowl, whisk the eggs, sugar, infused milk and oil together then add the baking powder and the flour. Mix in the smoked potato flesh.
Pipe the mixture in rings on to a baking tray lined with baking paper, then place in the freezer for 1 hour.
For the potato sugar, put 75ml water and the sugar into a saucepan and place over a high heat. Bring up to 160ºC then whisk in 70g of the reserved potato flesh and the food colouring until crystallised. Sprinkle on to a tray and once cool, add the popping candy and mix well.
Before serving, fill a saucepan ¾ full with oil and place over a high heat until the temperature reaches 180ºC. Remove the donuts from the freezer and fry until golden brown (approximately 5 minutes).
Dip the warm donuts into potato milk jam and sprinkle with potato sugar.