Belgian Fries (known as “Vlaamse friet” or simply “patat” in the Netherlands) are very popular in both Belgium and the Netherlands. The main difference with French fries is that they are thicker. Belgian fries should be freshly cut, fried twice, fluffy on the inside, crispy on the ouside, have a distinct potato taste, and are 1 cm (1/2 inch) thick. Belgian fries are usually served in a paper cone when you buy them from a street vendor, but at home I just serve them on a plate.
For the best taste, real Belgian fries must be fried in beef tallow (ossewit, rundvet, blanc de boeuf). Besides the flavor, this also has the advantage that the smoke point of beef tallow (255C/490F) is higher than of most vegetable oils used for deep frying (e.g. peanut oil 225C/440F), so the fat does not degenerate as much at the temperatures (up to 190C/375F) needed to fry.
In the Netherlands the use of beef tallow (ossewit) for frying has all but disappeared, thanks to health freaks claiming the low-cholesterol benefits of using vegetable oil. They are of course right that frying in vegetable oil is better for your cholesterol, but unlike vegetable oil, beef tallow does not contain any trans fat so it is not clear-cut which is more healthy. Fries are quite fatty in any case, but like I always say: I’d rather eat less of a tasty food than not eat it at all. So if you eat fries only once in a while like I do, I’d recommend to use beef tallow. Having said this, the recipe below will also work fine with vegetable oils with a high smoke point such as peanut oil. You will just miss out on the better taste. (Although ossewit is hard to find in Dutch supermarkets, some Albert Heijn or Jumbo supermarkets still carry it. Thanks to Kristien for locating ossewit in the AH Assendelft!)
The other important ingredients is of course the potato. Floury potatoes (“kruimig”) are best for fries. Since they contain less water than waxy (“vastkokend”) potatoes, the fries will be more crunchy on the outside and more fluffy on the inside. Large potatoes will give you longer fries and are less work (less peeling for the same weight of fries). The sugar content of potatoes is lowest when they have just been harvested, and increases slowly while they are stored. The sugar content increases more quickly when potatoes are stored in a colder place (e.g. your refrigerator). Since a higher sugar level will make the fries brown faster, you will get lighter fries with new potatoes and browner fries with older potatoes or potatoes that have been stored in the refrigerator.
Belgian Fries are usually served with mayonnaise, not with ketchup and definitely not with vinegar.
3 kilograms (6-7 lbs) beef tallow (substitute with 3 liters/quarts vegetable oil with a high smoke point)
Start by heating the beef tallow. Beef tallow is solid at room temperature, so you will need to melt it first.
In Belgium it is said that fries should ‘swim’, i.e. use enough fat so the temperature does not drop too much when you add the fries.
Here comes a very important step to obtain fries that are crispy on the outside and fluffy on the inside. Shake the fries well to remove as much of the fat as possible. Line a tray with paper towels, and spread out the fries. Let the fries cool to room temperature, and then refrigerate them for at least half an hour (or up to a day). The cooling and drying is important to make them crispy.
Do not fry more than about 500 grams (1.1 lbs) of fries at the same time, otherwise the temperature of the fat will drop too far. Fry in batches if needed, or use more fat (the fat should be at least 5 times the amount of fries).
In Belgium it is also said that fries should ‘spring’. This refers to the necessity to let the fries ‘jump’ for a bit. That is the the final important step to ensure crispy fries: toss them into the air a few times (making sure to catch them again in the colander…) so the salt is distributed evenly and the excess moisture can escape. That moisture would otherwise make the fries soggy.