To make the chocolate pudding:

1. In a medium heatproof mixing bowl, combine 1/2 cup of the whole milk, cornstarch, egg yolks, salt and espresso powder. Whisk until combined and smooth, and set aside.
2. Sift both of the cocoas into a saucepan or saucier, and stir in the brown sugar. Add the remaining 1 1/2 cups whole milk and whisk until smooth.
3. Place the cocoa/sugar/milk mixture over medium high heat and cook, stirring frequently, until the mixture simmers. Slowly stream the hot chocolate mixture into the egg/cornstarch bowl, whisking quickly and constantly to temper the eggs.
4. Once all of the chocolate mixture has been added to the eggs and incorporated, add everything back into the saucepan. Whisk constantly and cook over medium heat until thickened and bubbling, about 7-8 minutes.
5. Once the pudding is bubbling, continue to whisk for an additional minute before removing from the heat.
6. After the pudding is off the heat, stir in the melted chocolate, butter and vanilla extract until smooth. Strain the hot pudding through a fine mesh sieve and onto a large plate or shallow dish. Spread the pudding over the surface of the dish to create a thin layer, and then press a sheet of plastic wrap on top of the pudding to prevent a skin from forming.
7. Refrigerate the pudding for at least 2-3 hours, or until completely chilled.

To assemble the trifles:

1. Scoop 1/2 cup of the crumbled chocolate cake into each half pint jar, and pack down gently with the back of a cereal spoon.
2. Drizzle 1 teaspoon of Kahlua over the packed cake.
3. Spread 1 TB salted caramel sauce over the soaked cake.
4. Sprinkle 1/2 TB crushed Heath bar over the caramel layer.
5. Spoon 2 TB of chocolate pudding over the crushed Heath bar.
6. Make the whipped cream just before you need it. In a chilled mixing bowl, whip the cold heavy cream on high speed until soft peaks form. Add the powdered sugar and vanilla, and continue to whip until very stiff peaks form. You should have roughly 1 1/2 cups of finished whipped cream.
7. Spread 2 TB of the whipped cream on top of the chocolate pudding, and finish each trifle with another 1/2 TB of crushed Heath bar.
8. Seal the jars and refrigerate for at least 2 hours to allow the flavors to meld together.
9. Trifles will keep for up to a week when sealed and under refrigeration.