Set the oven to 350° F Beat the butter, sugar and eggs on medium speed until fluffy. In a separate bowl, combine the flour and cocoa powder.  Slowly add the flour mixture to the sugar mixture, beating well on medium to high speed.  Pour the batter onto a greased jelly roll sheet and sprinkle with almond slivers. Bake at 350° F for 20-25 minutes (the top layer will have a crackled texture while the bar itself will be moist) Allow to cool for 5 minutes and cut into squares.