In a bowl, combine the sugar and egg. Add the sifted flour and mix some more.
Once the batter is incorporated, add the baking powder. Add the milk (150 ml) in several batches, add the liqueur, and mix well.
If the dough from Step 2 is too thick and it is tough to whisk, add the remaining milk, a little at a time, to make it thinner.
The batter should be not too thick or not to thin, but needs just enough thickness as shown in this photo.
Form small balls using 2 small spoons, drop the batter into the heated oil at about 160-170℃, and slowly deep-fly.
The donuts should rise and start to spin around. They will turns into round balls and float to the top.
Sprinkle on some powdered sugar, and it they're done.
Story Behind this Recipe
This is one of the traditional snacks that people eat at carnivals in Italy. I reduced the amount of the original, since the recipe mamma gave me was too much. I also added some milk to the original recipe, to make the dough easier to handle.
The key is the oil temperature. If the oil is too hot, the insides of the donuts will be undercooked. If it is too cool, the donuts will absorb the oil, and become too dense.