Mix the dry yeast with 1 tablespoon of sugar and 50 ml of warm milk and leave to activate for about 10-15 min.
Sift the flour and mix it with the rest of the sugar, salt, and spices in a large bowl. Make an indent in the middle of the bowl with the dry ingredients and start adding the activated yeast, egg yolks, the rest of the milk, and melted butter. Add the whiskey or rum and the zest of one lemon and combine everything into a ball. Leave the dough to rest for 10 minutes covered with a damp kitchen towel. At this moment it's still sticky.
Now transfer the dough to a well-floured surface and knead for about 5 minutes. Avoid adding too much flour. The whole process of kneading can be done in a stand mixer.
When the soft dough is formed, lightly oil the bowl, put the dough inside, cover it with a damp kitchen towel and let it rest in a warm place until it doubles in size. This can take between 1-2 hours, depending on the temperature of the room.
On a well-floured surface, roll out the dough to a thickness of approximately 1 cm. Use a donut cutter for cutting the bigger circles and a bottle cap for the inner circles if you don't have the small donut cutter.
Sprinkle the donuts with some flour and cover them again with a damp kitchen towel. Let them rise for another 30-45 min.
Combine the rest of the dough back into a bowl and leave it covered with a damp kitchen towel for 10 minutes. Then roll it out again and cut out a few more donuts. These will probably be smaller and thicker when baked but still very delicious.
Heat the oil in a large pot, to a temperature of approximately 170-180°C. If you have a kitchen thermometer, use it in this step.
Carefully put the donuts in the hot oil and fry until they become golden brown, about 1 minute per side. When done, place them on a cooling rack covered with 2-3 layers of paper towel so the excess oil gets soaked up.