01 -
Preheat the oven to 350°F (177°C). Grease a 9 x 13-inch baking pan with nonstick spray or shortening and set aside.
02 -
In a large bowl, combine the cake mix, chocolate instant pudding, eggs, buttermilk, melted butter, and vanilla extract. Use a handheld mixer fitted with beaters to mix until all dry ingredients are incorporated, about 2–3 minutes. The batter will be thick.
03 -
Spread the batter evenly into the prepared baking pan. Bake for 25–30 minutes or until a toothpick inserted in the center emerges clean.
04 -
Transfer the baked cake to a cooling rack and let it reach room temperature, approximately 30 minutes.
05 -
Using the handle of a wooden spoon, poke holes into the cake spaced about 0.75 inch apart, aligning them along prospective serving lines for decorative effect.
06 -
In a medium bowl or measuring jug, whisk together the cold whole milk and Oreo pudding mix by hand or with a mixer for 1 minute, ensuring a smooth consistency with no lumps.
07 -
Immediately pour the prepared pudding over the cake, aiming to fill each hole thoroughly. Spread the pudding evenly over the surface and gently tap the pan to settle the filling.
08 -
Place the cake in the refrigerator uncovered for 1–2 hours to allow the pudding layer to set completely.
09 -
In a large bowl, combine heavy whipping cream and powdered sugar. Using a hand mixer with a whisk attachment, start at low speed for 30 seconds to blend, then increase to high and whip for 3–4 minutes or until stiff peaks form.
10 -
Evenly distribute half of the crushed Oreo cookies over the chilled cake. Spread the whipped topping evenly over the surface, then sprinkle with the remaining crushed Oreo cookies.
11 -
The dessert is ready for serving immediately once topped, or refrigerate uncovered for an additional 30–60 minutes before presentation.