Couverture chocolate
Couverture is professional chocolate with a raised cocoa butter content, at least 31%. That fat proportion is what separates it from ordinary eating chocolate and defines everything it is used for.
More cocoa butter means lower viscosity when melted. Couverture flows more freely and settles in a thinner layer, which is why it coats bonbons, casts shells and forms decorations — jobs where a thick shell would wreck the balance of flavour.
The same fat gives couverture, once correctly tempered, its pronounced gloss and clean snap.
Couverture must be tempered. Without it the cocoa butter sets in unstable crystal forms, and the chocolate comes out dull, soft, melting in the hand and prone to bloom.
It is produced in dark, milk and white; the latter two contain milk solids and melt at lower temperatures, so their tempering curves differ.