1. Preheat the oven to 350°F. Line an 8 x 8″ baking pan with parchment paper, allowing the sides of the parchment to extend over the sides of the pan by 1 to 2 inches for easy removal of the brownies once baked.
2. In a medium pot, add the bittersweet chocolate chips and butter. Melt over medium-low heat, stirring occasionally. Remove the pot from the heat once the chocolate and butter are melted and smooth.
3. Immediately sift the black cocoa powder into the chocolate and butter mixture, whisking to combine well.
4. Add the sugar and whisk continuously for 1 to 2 minutes. The mixture will be grainy.
5. Add the eggs and vanilla, whisking to combine well.
6. Add the flour and salt, folding the batter together with a large spatula or wooden spooon. 
7. Transfer the batter to the prepared pan, using an offset spatula to level the top. 
8. Bake in the center rack of the oven for 18 to 20 minutes or until the edges of the brownies are set and beginning to pull away from the sides of the pan. The center of the brownies should not jiggle when moved. 
9. Remove the brownies from the oven and cool in the pan on a wire rack. Once the brownies reach room temperature, use the parchment paper overhang to carefully lift the brownies from the pan. 
10. Slice into small rectangles and decorate.

Frosting

1. In the bowl of a stand mixer fitted with the paddle attachment (or using a hand mixer), beat together the butter, powdered sugar and salt on low speed until combined. Increase the speed gradually, mixing on medium-high speed for one minute.
2. Scrape down the sides of the bowl. Add the heavy cream (or whole milk) and mix to combine. Increase the speed to medium high and beat for 2 minutes. 
3. Use a spatula to stir the frosting, pressing it against the sides of the mixing bowl to eliminate any air pockets. If the frosting is too thick, add more milk. If too thin, add more powdered sugar. 
4. Transfer the frosting to a large piping bag fitted with a slatted piping tip. 
5. Pipe the frosting onto each brownie in a zig-zag pattern to resemble a bandage-wrapped mummy. Add two edible googly eyes to each brownie. If the frosting is soft, place the brownies in the refrigerator for 20 minutes to firm up.