Make the Pudding:

1. To a medium metal bowl, add the chocolate and the butter. Place a fine-mesh strainer over the bowl; set aside
2. In a medium pot, whisk together the sugar, cornstarch, black cocoa, and salt. Whisk in the egg yolks and milk until fully combined.
3. Turn on the heat to medium and cook the mixture, stirring constantly, until the pudding has thickened and large bubbles are forming and popping, about 8 minutes. 
4. Remove from the heat and immediately pour through the strainer into the bowl with the chocolate and butter, using a spatula to push all of the pudding through while leaving behind any bits of cooked egg.
5. Let the pudding sit for 2 minutes while the chocolate melts, then whisk it together until fully combined. Place a piece of plastic wrap or parchment on top of the pudding to prevent a skin from forming.
6. Let the pudding cool at room temperature before chilling in the refrigerator for at least 3 hours or overnight.

Make the Whipped Cream: 

1. Using an electric mixer, whip the cream cheese and granulated sugar until mostly smooth. Slowly drizzle in the heavy cream on low speed, then increase to medium and whip until the cream has reached soft stiff peaks, about 2 minutes more. Set aside.

Assemble the Cups:

1. Remove the chilled pudding from the refrigerator, discard the plastic wrap, and give it a whisk to loosen it up.
2. Using a food processor (or a rolling pin and a bag) crush the cookies (see note). Add 2 tablespoons of the cookie crumbs into each of 6 jars (see note about sizing), Using the back of a spoon (or something similar), press down on the crumbs to tightly pack them into the jars.
3. Spoon (or scoop) a heaping ¼-cup of black cocoa pudding into each jar.
4. Sprinkle 2 tablespoons of cookie crumbs on top of the black pudding in each jar.
5. Add half of the whipped cream to the remaining black cocoa pudding. Use a rubber spatula to fold it in until no white streaks remain.
6. Spoon (or scoop) a heaping ¼-cup of the whipped cream/pudding mixture into each jar.
7. Sprinkle the tops of each jar with 2 tablespoons of cookie crumbs.
8. Garnish as desired with gummy worms and/or remaining whipped cream.
9. Serve immediately.