Melt butter (or margarine) and cheese. (May be melted in the microwave or on top of stove. Do not overheat and/or scorch or burn the cheese. I prefer a double boiler on top of the stove as it is less likely to burn or scorch the cheese) After the butter and cheese are fully melted add nuts (if desired), cocoa, and vanilla extract and stir well. Sift powdered sugar into mixture 1/4 pound at a time. Mix well after each 1/4 pound UNTIL NO WHITE SUGAR IS SEEN. The sugar will tend to accumulate in the bottom so be sure and mix all the way to the bottom of the bowl and scrape the sides and bottom of the bowl often. The mixture will get extremely hard to mix by time the last two 1/4 pound(s) of sugar are introduce but be sure to mix well until no white is seen..
After mixing all the sugar put mixture in a 13 X 9 X 2 inch non-greased pan. (I use a throw away aluminum pan) Chill for about two or three hours, until the fudge is firm, then remove from pan and cut into bite size pieces. The fudge is hard to remove from the pan so I use a throw away aluminum pan and cut the pan on each corner and peel the sides away from the fudge. This leaves one large block of fudge which can then be sliced into smaller pieces. Keep refrigerated.
NOTE: Any flavoring may be substituted for the vanilla