They are already very tasty naturally, but you can also vary with extra ingredients to make the oliebollen completely to your own taste.
Examples of variations for Oliebollen:
Tip 3: 'Well and long soaking of raisins' click here for all tips for soaking raisins
Let the filling (raisins, currants) soak for 10 minutes and then rub dry.
Ideally you let them soak for an hour, then let them dry for a day and store them in the fridge until use. Raisins that have not been soaked well will draw moisture from the Oliebol and then the balls will become dry.
180 degrees Celsius.
Salad oil or sunflower oil work best. Peanut oil is also a possibility. Do not fry in frying fat or olive oil.
To slide the batter into the oil, you can use a moist gravy ladle or an ice cream scoop, which you occasionally rinse in water. If your batter is right, the balls will flip on their own. Often you can give fate a hand and turn the balls with a fork after a few minutes.
Before baking (after rising) stir the batter. If it has risen too much, the batter will be too airy = fat.
Don't make the mistake of making the batter in a bowl that is too small. For just a few euros you can buy a plastic washing-up bowl at, for example, the Blokker. Don't let it get out of hand!
And above all: often taste while baking!!! Then you know for sure whether they will be tasty enough!
First eat an Oliebol yourself. Place the Oliebollen on a nice dish, sprinkle some icing sugar on top and then walk into the room with your best smile and proudly say "Homemade!"

Read more about Oliebollen here (Wiki)