Preheat the oven to 350 degrees F and line an 8x8 baking pan with parchment paper.
In a large mixing bowl, whisk together the flour, sugar, cocoa powder, baking soda, and salt.
Add the eggs, milk, vegetable oil, and vanilla extract to the dry ingredients. Stir until smooth.
Carefully pour in the boiling water and mix until the batter is thin but fully combined.
Pour the batter into the prepared pan and bake for 30 to 35 minutes, or until a toothpick inserted in the center comes out clean.
Let the cake cool completely in the pan before spreading the chocolate frosting evenly over the top.
Sprinkle the crushed chocolate sandwich cookies over the frosting to create the dirt layer.
Press the rectangular chocolate cookies upright into the cookie layer to stand as gravestones.