
In a medium-sized saucepan, whisk together sugar, cornstarch, and salt.
In a separate mixing bowl (I use a large measuring cup), whisk together milk, cream, and egg yolks until yolks are broken up and ingredients are well combined.
While whisking the dry ingredients, slowly drizzle in the milk mixture and whisk until combined.
Cook over medium/medium-low heat, whisking constantly, until mixture has thickened to a pudding-like consistency and coats the back of a spoon (this will likely take around 10 minutes but could take more or less time depending on your stovetop).
Once mixture has thickened, immediately remove from heat and pour through a fine mesh strainer into a heatproof bowl. Add vanilla extract and butter and stir until butter is melted and completely incorporated.
Allow mixture to cool for 15-20 minutes, stirring occasionally, then press a piece of plastic wrap or parchment paper against the surface of the pudding and place in the refrigerator to cool completely, typically 1-2 hours, before moving on to the next step.
Once the pudding mixture has cooled, remove it from the fridge and set aside.
Place cream cheese in a separate, large bowl and use an electric mixer to beat cream cheese until completely smooth and creamy.
Gradually (a heaping spoonful at a time) add pudding to the cream cheese (I do this in 4-5 parts), mixing on low-speed after each addition until completely combined. Set aside.
Make the whipped cream: In a large, clean mixing bowl, use an electric mixer to beat cream and sugar until stiff peaks form.
Add the whipped cream into the pudding/cream cheese mixture, using a spatula to gently fold together until combined.
Evenly layer about half of the crushed cookies into the bottom of a 13x9” (33x23cm) pan and use the bottom of a glass or measuring cup to tamp down into an even layer.
Gently pour or dollop the pudding mixture evenly over cookie crumbs, then use the back of a spoon or an offset spatula to smooth into an even layer. Sprinkle the remaining crushed cookies evenly over the surface of the pudding. Cover tightly with plastic wrap and refrigerate for at least 2 hours before topping with gummy worms and serving.