Lewis Short
mustācĕus | mustācĕum, i (noun M.n) : m., and , , n.
* A must-cake or laurel-cake, a kind of wedding-cake mixed with must and baked on bay-leaves: mustaceos sic facito, etc.,Cato, R. R. 121; Juv. 6, 200.—Prov.: laureolam in mustaceo quaerere, to look for a laurel-wreath in a cake, i. e. for fame in trifles, Cic. Att. 5, 20, 4.
Charlton T. Lewis, Charles Short, A Latin Dictionary