Preheat the oven to 325. Line an 8 inch square metal baking pan with foil and grease the bottom only.
Combine the softened butter, sugar, cocoa and salt in a metal mixing bowl and set the bowl over a saucepan of gently simmering water. Stir until butter melts and mixture is fairly smooth and the sugar has partially dissolved -- mixture will still be slightly grainy. Remove from heat and let it cool to warm.
Stir in the vanilla, then add the eggs one at a time and stir after each egg is added.
Add the flour and stir until it disappears, then beat vigorously for 40 strokes with a heavy duty scraper.
Spread mixture evenly in the pan and bake at 325 for about 25 minutes or until brownies appear set. Let cool completely, then chill thoroughly.
Time for the fun part! Lift the brownies from the pan and cut into shapes using metal cookie cutters or whatever type cutter you have.
Melt chocolate in microwave using 50% power and stirring often until it is melted and smooth. Spread a very thin layer of chocolate on top of each brownie, then pile on some M&Ms. Drizzle more chocolate over M&Ms. Let the brownies sit until chocolate sets. Do not chill after adding M&Ms as they will lose their luster.