Preheat your oven to 350°F (177°C) and prepare three 8-inch cake pans by greasing and lining them with parchment paper.

In a large mixing bowl, whisk together the all-purpose flour, cornstarch, Dutch process cocoa powder, baking soda, baking powder, salt, and white granulated sugar.

In a separate mixing bowl, combine the vegetable oil, buttermilk, large eggs, and pure vanilla extract. Gradually mix in the hot water until smooth.

Pour the wet ingredient mixture into the dry ingredients and gently stir until just combined.

Divide the batter evenly among the prepared pans and bake for 20-24 minutes, or until a toothpick comes out clean.

Let the cake layers cool in the pans for about 10 minutes before transferring them onto a wire rack.

In a mixing bowl, beat the cream cheese and vanilla extract until smooth. Fold in the whipped heavy cream and crushed Oreos.

In a clean mixing bowl, beat the butter and cream cheese until fluffy. Gradually add the powdered sugar and then stir in the Oreo crumbs.

Heat the heavy cream in a saucepan until it simmers, then pour over the chocolate chips and stir until smooth.

Assemble the cake by placing one layer on a serving plate, adding filling, and repeating. Frost the outside and drizzle with ganache.

Decorate the top with whole or crushed Oreos, let it set before serving.