I love Dutch frites, and I particularly like the Flemish Frite Saus called vlaamse mayonnaise that they serve at the Frite shop called VleminckX Sausmeesters on Veotboogstraat (just one block off Kalverstraat, the main walking street down the center of Amsterdam).
What gives it that special kick. It's a bit more tart than American mayonnaise.
Best Answer
Frietsaus is just a special mayonnaise
Commercially it is lower in fat than plain mayonnaise
It has oil, starch (replaces extra oil), whole egg yolk, whole mustard seed, sugar, distiled vinegar, and lemon juice
So the kick is just the extra acid (vinegar and lemon juice), the bite from the whole seed mustard, mixed into a lite sauce, not a heavy greasy mayo
BTW: VleminckX Sausmeesters is just a touristy thing, there are plenty of shops in Holland that serve great fries
Personally I think that potatoes from Europe are a bit plain compared to many other continents/countries. the best I have had are from Fiji, the warm humid conditions make excellent deep frying potatoes, and I suspect they lace the cooking oil with a little coconut oil too :-)