Definition of "malvoisie"

Now this Malvoisie has a body, and slips down the red lane with an unctuous savour; […]

1852, The Royalist and the Republican, volume 1, page 108

Adrian stood and refilled Shelagh's glass. ‘A little more malvoisie for you?’

1991, Stephen Fry, chapter XIV, in Liar

There, gifts were exchanged […] and Philip's mistrels performed in front of the king's mother who sat, appreciative, her customary glass of malvesey to hand.

2011, Thomas Penn, Winter King, Penguin, published 2012, page 217