Preheat the oven to 350°F.
Line two cookie sheets with parchment paper. Set aside.
Use a rolling pin to roll out both pie crusts. Sprinkle with a tiny bit of flour to keep the dough from sticking to the counter. Try to roll the dough so it becomes a square. It's easier to cut the rectangle shapes that way.
You can use a pastry wheel or knife to cut rectangles into the dough. They should be pop tart sized with enough room to stuff chocolate caramel pieces inside each one.
Grab your cookies sheets and place half the rectangles on them, spacing them about an inch or two apart. Then, carefully place 2 to 4 pieces of Caramilk in the middle of each rectangle. If you want them to taste more like Samoas you can add a tablespoon of coconut to each one. That's completely optional.
Whisk the egg and water (or milk) in a small bowl. Then, brush a small amount of that egg wash around the top edges of the dough. Set the egg wash aside, you'll need it again.
Place the top pieces of dough on each one and press down slightly. Gently press the edges down with your fingers, then use a fork dusted with flour (or water) to press down and seal the edges properly. A pastry wheel can be used to trim any uneven pieces.
Use a fork and gently poke a few holes in the tops of each pop tart. Them brush the tops with the remaining egg wash.
Place the cookie sheet in the preheated oven, and bake for about 8 to 12 minutes. They should be a light golden brown when done. Remove from oven and repeat the process with the second cookie sheet.
Allow tarts to cool slightly on the pan for a minute or two, then transfer to a cooling rack to et them cool completely.
While the pop tarts are cooling you can make the Nutella ganache.
Measure and transfer the Nutella to a medium size bowl. Set aside.
Use a small saucepan over medium heat to heat the heavy cream until it just starts to bubble. Once it comes to a boil you can quickly pour it over top of the Nutella you placed in the bowl. Whisk that mixture until it starts to thicken. Add more Nutella if you want it thicker, or you add more heavy cream if you want it thinner.
Allow the ganache to cool for about 3 to 5 minutes. Use an offset spatula to smooth the Nutella ganache over each pop tart. Toss or gently place some sprinkles over top while the ganache is still wet so they stick properly.
Serve or store for later.