In a small bowl, stir together the yeast and warm water. Leave until frothy, about 10 minutes.
In a large mixing bowl, put the flour, milk, butter, eggs, sugar, cinnamon and salt. Pour in the yeast mixture and mix until everything starts to come together.
Form the dough into a ball. It will be rather sticky but don’t be tempted to add more flour or you will have very dense instead of soft and airy donuts. Place in a clean bowl, sprinkle the top with flour, then cover the bowl with a kitchen towel. Leave to rise until double. Depending on the room temperature and humidity, this can take anywhere from two to three hours.
Sprinkle the work surface with flour. Turn out the dough. Dust your rolling pin with flour (unless you have one of those pretty non-stick models) and roll the dough to about half an in thick.
Using a three-inch round cutter, cut out circles.
Use a smaller cutter to cut out the holes. If you have a donut-cutter, the process would be simpler. We don’t so we just used the multi-sized steel cutter that we have (and which I keep forgetting to take photos of so I can show you).
Lift the dough so that only the cut pieces are left on the work surface.
Sam re-rolled the dough and made donut twists.
Heat the cooking oil. The ideal temperature is 350F but I don’t have a thermometer for that job (the only ones I have are for meat and to measure the oven temperature). To test if the temperature is correct, drop a piece of dough into the hot oil. The dough will sink to the bottom, if it does not rise after a few seconds, the oil is still not hot enough.
If the dough browns too fast within seconds from touching the hot oil, the oil is too hot. Lower the heat and wait a few minutes.
Fry the donuts in batches, two to three at a time, depending on the size of your pan. One minute per side is quite enough. Flip them to brown the other side.
Scoop out the browned donuts and drain on paper towels.
Roll them in plain sugar (or add cinnamon and nutmeg to the sugar for more aromatic donuts) or dip one side in ganache for chocolate-topped donuts.