Step 1: Prepare chocolate cake according to package directions. Bake and let cool completely on a wire rack. Once cooled, cut the cake into 1-inch cubes.
Step 2: In a large bowl, whisk together the instant vanilla pudding mixes and cold milk for 2 minutes. Add green gel food coloring until a vibrant, eerie green is achieved. Stir well. Refrigerate for at least 30 minutes, or until set.
Step 3: In a separate large bowl, beat the heavy whipping cream, powdered sugar, and vanilla extract with an electric mixer until stiff peaks form.
Step 4: Gently crush the chocolate sandwich cookies (without the cream filling) in a food processor until they resemble fine dirt. Set aside.
Step 5: To assemble the trifle, place half of the chocolate cake cubes in the bottom of a large trifle bowl (about 4-quart capacity).
Step 6: Carefully spoon half of the green pudding mixture over the cake layer, spreading evenly.
Step 7: Spread one-third of the whipped cream mixture over the pudding layer.
Step 8: Repeat with the remaining chocolate cake cubes, then the remaining green pudding, and another third of the whipped cream.
Step 9: Top with the remaining whipped cream, smoothing the surface.
Step 10: Sprinkle the crushed cookie “dirt” generously over the top of the trifle, covering the whipped cream completely.
Step 11: Decorate with gummy worms peeking out of the “dirt,” candy pumpkins, and chocolate wafer cookies carved or decorated to look like gravestones. Get creative with your spooky scene!
Step 12: Refrigerate the spooky halloween trifle recipe for at least 4 hours, or preferably overnight, to allow the flavors to meld and the cake to soften. Serve chilled.