A five-year-old from a named grape is the floor for drinking; cheap 'cooking' Madeira is caramel-coloured and flat.
A little history
The heating copies what happened to barrels on long voyages through the tropics, which were found to improve the wine.
Worth knowing
It barely changes once open, so it's the fortified wine to keep on the back shelf. Sercial or Verdelho as the vermouth in a stirred drink; Bual in a sauce for beef.