Prepare the Oreo crumbs. Working in batches, place the two packages of Oreo cookies in a food processor and pulse until they are reduced to fine crumbs. Transfer all of the crumbs to a large bowl and reserve them for assembling the desserts.

Prepare the chocolate pudding filling. Pour the 4 cups of cold whole milk into a large mixing bowl and add both packages of instant chocolate pudding mix. Whisk for approximately 2 minutes, or until the pudding begins to thicken.

Incorporate the whipped topping. Carefully fold the 16 ounces of thawed whipped topping into the thickened pudding until evenly blended and no visible streaks remain.

Add the first portion of chocolate syrup. Drizzle 1/2 cup of the chocolate syrup over the pudding mixture. Fold or swirl it gently only a few times, leaving visible ribbons of syrup throughout the filling rather than blending it completely. Refrigerate the mixture until assembly.

Begin assembling the cups. Arrange 18 serving cups, each with a capacity of approximately 9 ounces. Spoon 2 tablespoons of the Oreo crumbs into the bottom of every cup.

Add the pudding layer. Place slightly less than 1/4 cup of the prepared chocolate pudding mixture over the first crumb layer in each serving cup.

Repeat the layers. Add another 2 tablespoons of Oreo crumbs to each cup, followed by the remaining pudding mixture. Finish each portion with 1 tablespoon of fine Oreo crumbs on top.

Prepare the moist “fresh dirt” crumbs. Transfer the remaining Oreo crumbs to a small bowl and stir in the reserved 1/2 cup of chocolate syrup. Mix until the crumbs become moist, irregular, and slightly clumped. Set them aside for the final decoration.

Create the gravestones. Using the black decorating icing, write “RIP” or other Halloween-themed wording on the Milano cookies. Carefully insert the decorated cookies into the tops of the dessert cups so they stand upright like grave markers.

Add the Halloween decorations. Position the ghost-shaped marshmallow treats and mini pumpkin candies on top of the cups, pressing them gently into the surface so they remain upright.

Finish the graveyard effect. Scatter assorted Halloween sprinkles over the desserts, then distribute some of the clumpy chocolate-cookie mixture around the decorations to resemble freshly disturbed soil.

Chill and serve. Refrigerate the completed Graveyard Dirt Cake Cups until serving time, or serve them immediately after decorating.