I have been a pro pastry chef most of my llife now. But I don't know much about these super high gloss individual cakes as seen in top London stores. Can anyone tell me something about them?
High gloss icings
It definitely would be helpful to have a picture to see exactly what you're talking about. Depending on what kind of cake, high gloss can be achieved in any number of ways. For instance, for chocolate dessert items, you can make a chocolate mirror glaze. Other dessert items can be "glossed" with fruit and clear glazes.
High gloss glazes are usually achieved with copious amounts of gelatin, sometimes pectin, and usually in combination with corn syrup.
Traditional high gloss finishes--some going back centuries, are achieved with gum Arabic or food grade laquer.