Melt the chocolate and butter in a saucepan over medium-low or low heat.
In a large mixing bowl, combine the sifted powdered sugar and eggs, mixing well but carefully, as it dusts up quite a bit!
Add the melted chocolate mixture and vanilla extract to the bowl with powdered sugar and eggs. Mix thoroughly to incorporate
Add the nuts if desired and mix to thoroughly incorporate.
With a spatula, pour chocolate fudge mixture into a well-greased 8x8" pan. Refrigerate for at least 3 hours, or until firm. Slice into (64) bite sized pieces and serve. Refrigerate when it's not being served.
Notes
The risk of getting salmonella from a raw egg is about 1 in 20,000. Pasteurized egg products are an excellent alternative to raw eggs. The eggs are pasteurized right in the shell using patented all-natural processes to kill the bacteria effectively so that salmonella is no longer an issue. So, pasteurized eggs are completely safe to use uncooked. There is a great way to do it yourself if you can't find them at your market. Read about it here from my friend Liz, over at her blog, Sugar Geek Show.
Nutrition shown is per piece of fudge without nuts.