Hungarian and Viennese in origin, and named after Rigó Jancsi (1858-1927), a famous Hungarian Romani violinist. His good looks and fiddle so charmed Clara Ward, daughter of E.B. Ward of Detroit, the 'steamship king of the Great Lakes' while playing for her in a Paris restaurant that she left her husband, Prince Joseph de Caraman-Chimay and ran off and married him. The newspapers at the time couldn't get enough of it.
The cake (it's uncertain with Rigó invented it or it was just named after him after he bought one) usually has a dense chocolate layer and a thin layer of apricot jam between the chocolate sponge, and is topped with a dark chocolate glaze.
Images by: Antidiskriminator, Public Domain