This was the recipe card included in Gussie's files.

Melt butter and marshmallows. Original recipe said double boiler, but you could probably do this in the microwave.
In a large mixing bowl, combine the remaining ingredients.
Add the marshmallow mixture and mix by hand.
Press into a loaf pan lined with wax paper.
Refrigerate 24 hours before serving.
If desired, flavor with rum or brandy.