Boil potatoes with skin on for about 30-40 minutes until tender when poked with a fork. Let cool.
While potatoes are cooking prepare the starter
In a small bowl mix ½ cup flour with yeast, add milk and stir until creamy consistency. Let sit for 30 minutes until the mixture starts to bubble.
Prepare the dough
In a large bowl sift all the remaining flour, add the starter, sugar, and potatoes passed through the finest disk of a potato ricer. Alternatively, you can grate potatoes. Give a quick mix, then add slightly beaten eggs mixed with zest from 1 orange and 1 lemon. Mix again. Lastly, add orange juice.
Using a dough hook on your stand or hand–held mixer knead the dough on low speed adding butter in small pieces. Wait for a piece of butter to be absorbed before adding the next piece.
Once all butter is incorporated place the dough on lightly floured surface stretching it into a rectangular. Starting with the bottom side, fold dough into thirds, like a letter. Do the same with the sides. You should get a tight, slightly irregular ball of dough.
Arrange it in a large slightly oiled bowl, cover with plastic wrap and let rise until almost triple in size.EXTRA TIP: while the dough is rising, cut parchment paper into squares slightly bigger than the size of the large cookie cutter you'll use to cut out the donuts. Prepare about 21-23 pieces.
Form The Donuts
Once the dough has risen, gently transfer it on a floured work surface. Roll to a little less than ½ inch (1 cm) thickness.
Using large (3 ½ inch - 9 cm) round cutter cut out donuts, cut out the center of each with a small (1 ⅓ inch - 3 cm) cutter.
Place each doughnut on a piece of parchment paper (slightly larger than the doughnut).
Arrange preferably in a deep baking sheet (or tray) slightly distanced apart. Cover with plastic so that the donuts won’t dry out.
If you have shallow baking sheet simply place 2 cups/glasses distanced apart. Arrange donuts then cover with plastic, the cups will create extra hight and prevent the dough from sticking to plastic bag.
Let rise for 1-2 hours or until double in size.
Fry and Roll In Sugar
When ready to fry, heat vegetable oil in a deep panto 355-360F (180C). Take each donut together with parchment paper and carefully put in hot oil. After about 1 minute remove the parchment paper with tongs. Once the doughnuts are fried on one side flip them over and continue frying on the other side until lightly golden brown. Transfer to a tray lined with paper towels to absorb excess oil.
Roll freshly fried donuts in granulated sugar. It’s best if someone can give you a hand doing this while you’re continuing to fry the donuts. DO NOT let donuts cool, sugar will not stick to cool donuts.Enjoy warm!
Notes
Dough scraps. Once you've used up all the dough to cut out the doughnuts out all dough scraps together. Knead very slightly just until you have a rough ball (do NOT add more flour). Let rest for 20 minutes. Now you can roll it out again and form more doughnuts.
Frying temperature. The best oil temperature for frying doughnuts is about 356F (180C). If the oil is too hot donuts will burn on the outside quickly and remain still raw inside. If the oil temperature is too low doughnuts with absorb oil and oily doughnuts is the worst thing you can have.
Use a large pan and enough oil! This might sound contradictory but the more oil you have in the pan when frying the LESS oily your donuts will be. More oil in the pan means the temperature will not go down so abruptly when you place a few doughnuts to fry. For this very reason the more doughnut you want to fit in one go the bigger your frying pan should be. Mine is almost 13" (32cm) and I use almost 2 quarts (2 liters) of oil. I also like to wait for about 10 seconds between the doughnuts.
Don't overcrowd the pan. If you have a smaller pan simply fry 2 doughnuts at a time.
Coat with sugar ASAP. If you wait for the doughnuts to cool the sugar simply won't stick so coat them asap after frying. Ideally have someone help you with that while you continue to fry the rest of the doughnuts.
STORAGE: in the unlikely event you have any leftovers store them in airtight container at room temperature for up to 2 days. When ready to eat, reheat in a non stick pan with lid on on low heat. Sugar coating will be melted by this time so you can simply dust graffe with powdered sugar to bring back the extra sweetness.FREEZING: just for the purpose of giving you all the details I've frozen graffe a few times and they hold really well. Let them thaw first then reheat as described above.For the best result use kitchen scale to measure all ingredients in grams.