In a bowl of a stand mixer fitted with a dough hook, combine all the donut dough ingredients. Turn the mixer on low and combine until it forms a thick but slightly sticky dough. Once combined, keep mixing on medium speed for around 8-10 minutes until the dough is smooth, glossy, and elastic.

Place the dough ball in a lightly greased large bowl. Cover the bowl with plastic wrap or a lid and place it in the refrigerator for anywhere between 4 and 24 hours. The longer it’s left, the more flavor in the donuts. If you want to skip the cold proof and make these donuts fast, let the dough double at room temperature instead (around 1- 1 1/2 hours). Then continue with the shaping.

Punch down the dough and pull it from the bowl onto a floured work surface or on parchment paper.

Using a rolling pin, roll the dough into a ½ inch / 1.3cm thick square. Use a doughnut cutter, cookie cutter, or a jar lid or glass to cut out the donuts.

Place the cut donut rings and the donut holes on parchment paper. Use kitchen scissors to cut around each donut on the parchment paper so each donut is sitting on an individual piece of parchment.

The donuts can be transported into the oil on parchment paper, which makes transferring them easier. If you don't have parchment paper, you can transfer the donuts without it.

Any remaining dough can be rolled out and cut again. Bombolini-style donuts - You can also simply cut them as circles and use a large jar lid or cookie cutter to cut circles of 3.5 inches/9 cm diameter, without a donut hole in the middle. These will be cooked slightly longer and at a lower temperature than donuts with a donut hole removed from the middle.

Leave the donuts to slightly rise for around 30-45 minutes until they have puffed a bit. This timing is dependent on room temperature – the warmer the room, the faster they’ll rise.

When the donuts have risen, pour the frying oil into a deep fryer or a deep pot and heat it to 356°F/180°C. The oil in the pan should be at least 3 inches deep. Note- if your donuts were cut without a donut hole (bomboloni-style), your oil should be less hot, 340°F / 171°C as they will take longer to cook in the middle so you don't want them going brown too fast on the outside.

If using a cinnamon topping, combine the granulated sugar and cinnamon in a small bowl and set it aside.

When the oil is at temperature, fry the donuts, only 2-3 at a time in the hot oil. Use tongs to remove the pieces of parchment paper from the oil.

Don't add too many at a time because they will lower the oil temperature. If it drops too much your donuts won't fry well and will absorb too much oil. Don't let the temperature surpass 375°F / 190C.

Fry the donuts for around 45-60 seconds on each side, so each side is a deep golden brown. It will be much less for the smaller donut holes. Bomboloni-style donuts will need around 2 minutes on each side.

After frying, use a slotted spoon to remove the donuts from the oil, then place them while hot, into the sugar bowl. Use tongs or two forks to flip the donuts in the sugar to coat them on all sides. Place the coated donuts on a wire rack, then repeat the process with the remaining donuts. 

If you are glazing the donuts, in a bowl, combine powdered sugar, vanilla, and enough to create a thick but pourable glaze. When the donuts come from the oil, place them on paper towels to soak up excess oil. Let the donuts cool on a cooling rack for 5 minutes, then dip the still-warm donuts into the glaze. Let them dry on the rack.