Preheat the oven to 350°F (175°C). Grease and flour two 9-inch round cake pans.
In a large mixing bowl, sift together the all-purpose flour, unsweetened cocoa powder, granulated sugar, baking powder, baking soda, and salt.
Add the eggs, whole milk, vegetable oil, and vanilla extract to the dry ingredients. Beat on medium speed for 2 minutes until well combined.
Stir in the boiling water carefully; the batter will be thin.
Divide the batter evenly between the prepared cake pans.
Bake for 30 to 35 minutes or until a toothpick inserted into the center comes out clean.
Remove the cakes from the oven and allow them to cool in the pans for 10 minutes.
Turn the cakes out onto wire racks and cool completely.
To make the Oreo frosting, beat the softened unsalted butter on medium speed until creamy, about 2 minutes.
Gradually add the sifted powdered sugar and unsweetened cocoa powder, beating on low speed until combined.
Add the heavy cream and vanilla extract, then beat on high speed for 3 minutes until light and fluffy.
Fold in the finely crushed Oreo cookies gently until evenly distributed.
Place one cake layer on a serving plate and spread a thick layer of Oreo frosting on top.
Place the second cake layer on top and frost the top and sides with the remaining Oreo frosting.
Refrigerate the cake for at least 30 minutes before serving to set the frosting.