Slice the potatoes on the mandoline slicer - be careful with your fingers.
Fill a bowl with water.
Put the mini fries in the bowl of water.
Let them sit in the water for 30-60 minutes. This is done to extract the starch from the potatoes, which helps to make them crispy. Feel free to replace the water with fresh tap water a couple of times during the process.
Lay a kitchen towel on the table.
Place the mini fries on one half of the kitchen towel.
Fold the rest of the towel over the fries and pat/dry them well. If you have time, you can advantageously put them in the freezer for 30-60 minutes - it helps to dry them out.
Pour oil into the fryer.
Set the fryer to 185 degrees Celsius (365 degrees Fahrenheit).
Deep-fry the fries at 185 degrees Celsius (365 degrees Fahrenheit) until they are crispy. It takes a few minutes, and it's important not to put too many in the oil at once, as it lowers the temperature. I made mine in three batches.