Hi Emily,
This is the one my Mom always made, hope it's what you are looking for.

Old Fashioned Fudge

3 cups granulated sugar
1/2 cup Cocoa
1 (12 oz) can evaporated milk
1 teaspoon vanilla flavoring
1/4 cup margarine or butter
1/2 cup nuts chopped (optional)

Completely mix sugar and cocoa together in large non-stick pan. Add milk and stir 'til completely mixed in with cocoa mixture. Place over medium heat; stirring constantly bring to a boil and continue boiling and stirring until mixture reaches 240 degrees on a candy thermometer. Stir in butter and vanilla. (If desired stir in nuts, now). Pour into greased 9x9x2-inch pan. Chill 'til hardened, cut into desired size pieces.