1. Preheat your oven to 350°F (175°C). Grease and flour two 9-inch round cake pans.
2. In a large mixing bowl, combine flour, sugar, cocoa powder, baking powder, baking soda, and salt. Stir until well mixed.
3. Add eggs, milk, oil, and vanilla extract to the dry ingredients. Beat on medium speed for about 2 minutes. Stir in boiling water (batter will be thin).
4. Gently fold in the crushed chocolate sandwich cookies, taking care not to overmix.
5. Pour the batter evenly into the prepared cake pans. Bake for 30 to 35 minutes, or until a toothpick inserted into the center comes out clean.
6. While the cakes are baking, whip the heavy cream and powdered sugar until soft peaks form. Set aside in the fridge until ready to use.
7. Once the cakes are baked, cool them in the pans for about 10 minutes, then remove from the pans and let them cool completely on a wire rack.
8. To assemble, place one cake layer on a serving plate. Spread a generous layer of whipped cream over the top, then sprinkle with additional crushed cookies.
9. Place the second cake layer on top, and frost the top and sides with the remaining whipped cream. Garnish with more crushed cookies if desired.

Remember, the key to a perfect cake is patience. Allow your cakes to cool completely before frosting to avoid a drippy mess. And don’t be afraid to get a little creative with your decorations!