Using whisk attachment on electric mixer, whip eggs and sugar until light and fluffly.
Fold chocolate mixutre into egg mixture just until incorporated. (do not overmix)
Gentlly fold in walnuts if you are using them.
Spread mixture into a parchment lined 9" baking pan and bake at 350 for 50-60 minutes.
Cool on wire rack,
Mix ingredients for frosting and spread thickly on cooled brownies.
Cut into bars of desired size.
Decorate with skeleton parts and chocolate cookie crumbs as desired
Notes
To make chocolate skeletons you will need a chocolate mold of skeleton parts. Melt white or orange chocolate pieces over double boiler. Pour into molds and chill until set (about 30 minutes).Store in airtight container at room temperature for up to 3 days.