Mooseburger (1961); Beef Wellington (1967 cite)

[jdespres at MERRIAM-WEBSTER.COM]

Here's a slightly earlier cite for Beef Wellington:

Beef Wellington, through some quirk of fashion, has become the
"in" dish this season.  It is a fillet of beef embellished with pate de
foie gras, truffles and cognac and wrapped in a rich pastry.  One
factor contribution to its popularity may be that it is equally good
served hot at the dinner table or cold on buffet tables.

Jean Hewitt
The New York Times Magazine
December 26, 1965

Joanne Despres
Merriam-Webster, Inc.