To make the caramel sauce, place a sealed, unopened can of sweetened condensed milk in a large pot and fully cover in water.
Boil the can for 2 hours, making sure to keep it covered in water the whole time. Set a timer and check it every half hour and add water to the pot if necessary. If the pot were to boil dry, the can could explode, which would be dangerous, so be sure to boil it carefully. After two hours remove from the water and allow to cool slightly. Remove the lid, and the insides will have turned into caramel sauce. Note: we only used half of the finished can for this recipe. This process is quite time consuming so be sure to do it first thing or even the day before, and give it some time to cool before using it.
To Make the Apples
Combine the sliced apples, brown sugar, ground cinnamon, nutmeg, and vanilla in a saucepan, and sauté apples over medium heat until the apple cinnamon mixture has softened about 5-6 minutes. Let the apple mixture cool slightly before adding to the trifles.
To Make the Custard
Whisk the egg, and egg yolk with the sugar. Add in the flour, cornstarch, and salt. Whisk until the mixture becomes pale yellow.
Heat the milk in a large saucepan over medium heat until the milk is hot but not boiling. Add ¼ cup of the hot milk to the egg mixture and whisk milk quickly to combine. Then add another ¼ cup of the hot milk and whisk quickly again. Slowly add the rest of the hot milk to the egg mixture, whisking quickly the whole time.
Add the egg mixture to a clean saucepan and return to a medium-low heat, whisking continually until the mixture begins to thicken and boil.
Remove from the heat and whisk in the vanilla, continue whisking until smooth. Allow to cool.
To Make the Whipped Cream
Add heavy cream or sometimes called whipping cream to a stand mixer, or pour into a large mixing bowl and use an electric mixer and mix on high speed until soft peaks form.
Add sugar and vanilla, and continue whipping until firm peaks form.
To Assemble the Trifles
In four mason jars, add a layer of cubed cake, about ⅓ of the jar.
Next, add a layer of custard.
On top of the custard add a layer of the apples.
Next, add a layer of caramel sauce.
Finally finish the trifles with a layered of whipped cream and chopped pecans.