To make the taco filling, set a medium skillet over medium-high heat. When hot, add the ground beef and start to break it apart into crumbles. (If using ground turkey or chicken, warm a drizzle of olive oil in the skillet first.) Add taco seasoning and shredded carrot or pepper, if using. Cook for 5-6 minutes, until the meat is browned, continuing to break it up into small pieces as you go. Remove from the heat and set aside.
Preheat the oven to 425 degrees F and line two large baking sheets with parchment paper or silicone baking mats.
Roll out the pie crusts on a pastry mat or the counter lightly dusted with flour. Use ghost-shaped cookie cutters to cut out shapes, being sure to have an even number — you’ll need one for the top and one for the bottom of each taco pie. Gather and roll out the scraps until all the pie crust is used.
Arrange half of the cut ghost shapes on the pastry mat, leaving some space around each. Spoon a small amount of the taco filling into the middle of each ghost, then sprinkle a bit of cheese on top.
Use anything small and round to cut out eyes and/or a mouth from the remaining ghost shapes. (I used the lid of a Crayola marker!) Place one of the shapes with a cut-out over each filled ghost on the baking sheets, then use the tines of a fork to gently seal all the edges.
Mix the egg with a splash of water or milk in a small bowl to make an egg wash, then brush this on top of each mini pie.
Bake for 10-14 minutes, until the tops are golden brown. Remove from the oven, let cool for a minute or two, then serve with salsa or guacamole for dipping. Enjoy!