Preheat the oven to 350°F and line a small 8x4 inch loaf pan with parchment paper.
In a mixing bowl, stir the melted butter and sugar together until smooth.
Add the eggs and mix until fully combined.
Stir in the flour, cocoa powder, and salt until no dry streaks remain.
Add green gel food coloring a drop at a time and mix until the batter reaches a bright green shade.
Pour the batter into the prepared pan and spread it evenly.
Bake for 22-25 minutes until a toothpick comes out with a few moist crumbs.
Let the brownies cool completely in the pan, then lift them out and cut into 4 rectangular bars.
Spread a thin layer of chocolate frosting on top of each bar.
Press two candy eyes into the frosting on each bar while it is still soft.
Use black gel icing to draw a jagged mouth and a few stitch lines below the eyes.