In a small saucepan over medium heat, whisk together the cornstarch, sugar, cocoa powder and salt. Whisk in the milk until fully incorporated.

Bring milk mixture to a light boil over medium heat. Cook, whisking constantly, until the mixture thickens to your desired consistency, about 5 to 9 more minutes. If mixture is not thickening to your liking, add cornstarch 1 tablespoon at a time until your desired consistency is reached. (Pudding will also thicken further upon chilling.)

When desired consistency is reached, remove saucepan from the heat. While whisking quickly, add the melted chocolate and vanilla. Immediately pour into a single serving bowl or into individual cups.

Generously top pudding with crushed cookies and arrange gummy worms on top. Chill until ready to serve.

Optional kid-friendly activity: To make a fairy garden or Halloween graveyard, decorate shortbread cookies (like ladyfingers) as rocks, trees, flowers, and/or creepy headstones and perch them in your dirt pudding creation.