This one is whacky.
Also there was this on the recipe card: "From recipe chain letter - Anna McReynolds' friend".
Also, at the bottom, it said: "(Very good)".

Mix butter and sugar.
Add 3 egg yolks and half of the flour.
Mix well and beat.
Add remaining egg yolks and remaining flour.
Beat the egg whites until stiff.
Fold egg whites into the batter.
Put in pan and cook 1 hour slowly*. (The original recipe card has no temperature, so let's go with 350°.)

*"Cook slowly"??? WTF does this mean?