Lord, i do believe the "White sauce" you speak of which is used with fish is called "Tartar sauce". And it is beautiful

Tartar sauce that's it. Yes it is great. Properly made. My father used to make his own from home grown herbs which was superb.

Echo both of you, you either love or hate it .. well .. strangely I'm in middle. I sometimes like it when in mood. And it is a yeast extract, obviously giving it the sharp flavor it has. It's supposed to be applied very thinly. But some people trying it for first time use lots & get a culture shock rock them & never touch it again. When applied lightly, it still has a touch of sharpness in flavor yet a subtleness as well.