Place 24–30 Oreo cookies into a food processor and pulse until you have fine, dark crumbs that look like soil — about 30 seconds to 1 minute. Transfer crumbs to a bowl and set aside. Checkpoint: You are ready to move on when crumbs are mostly fine and uniform with just a few slightly chunkier pieces.

Pour 3 cups of cold whole milk into a large bowl. Add both packages of instant chocolate pudding mix. Whisk vigorously for exactly 2 full minutes. The mixture will thicken noticeably. Let it sit undisturbed for 5 minutes at room temperature. Checkpoint: You are ready to move on when pudding mounds slightly on a spoon and holds its shape.

If using cream cheese, beat 4–8 oz of softened (room temperature) cream cheese in a separate bowl with a hand mixer until completely smooth with no lumps — about 1–2 minutes. Fold the beaten cream cheese gently into the set pudding using a rubber spatula.

Scoop the fully thawed Cool Whip into the pudding bowl in two separate additions. Use a rubber spatula to fold it in gently — do not stir or beat. Fold just until no white streaks remain, about 1–2 minutes total. The mixture should look light, airy, and mousse-like. Checkpoint: You are ready to move on when the mixture is uniform in color with no visible white streaks.

Place the pudding mousse into the refrigerator for 15–20 minutes to firm up slightly. This makes layering much cleaner and easier.

Set out 8–10 clear 9 oz plastic or glass cups. Add 1–2 tablespoons of Oreo crumbs to the bottom of each cup. Tap the cup gently on the counter to level the crumbs.

Spoon about 1/2 cup of the chilled pudding mousse over the crumb base. Tap the cup again to level the layer. Add 1 tablespoon of Oreo crumbs on top of the pudding. Tap to level.

Add a final layer of about 1/4 cup pudding mousse. Finish with a generous layer of Oreo crumbs across the top so the surface looks like dark soil. Tap one final time to settle everything. Checkpoint: You are ready to move on when you can see distinct dark-light-dark layers through the sides of the clear cup.

Cover each cup loosely with plastic wrap. Refrigerate for at least 30–60 minutes, or up to 2 days ahead. If making more than a few hours ahead, store the top crumb layer separately in an airtight bag and add it just before decorating.

Just before serving, melt 1/2 cup of chocolate chips in the microwave in 20-second intervals, stirring between each, until smooth. Transfer to a small piping bag or zip-top bag with a tiny corner snipped. Pipe "RIP" onto Milano cookies and let set for 2–3 minutes.

Insert the Milano tombstones upright into the Oreo crumb top of each cup. Press gummy worms partially into the crumbs so they look like they are crawling out of the dirt. Add candy eyeballs and any additional Halloween candy decorations. Serve immediately.