Start by rolling out your pie crusts on a floured surface to about 1/8 inch thick. Using a 4-5 inch ghost-shaped cookie cutter, cut out 20-24 ghost shapes and carefully transfer them to a baking sheet lined with parchment paper.

In a skillet over medium heat, brown the lean ground beef until fully cooked and no longer pink, about 6-8 minutes. Drain any excess fat, then add taco seasoning and optional veggies. Cook until the vegetables are tender, about 3-4 minutes, then mix in shredded Mexican cheese until melted. Allow filling to cool.

Preheat your oven to 400°F (200°C). Place half of the ghost-shaped crusts on a lined baking sheet. Spoon 2-3 tablespoons of cooled taco filling into the center of each ghost, leaving a border around the edges.

Beat an egg with a splash of water to create an egg wash. Brush the edges of the bottom crusts with this mixture. Place the remaining ghost shapes on top, pressing the edges to seal tightly, then crimp with a fork. Brush the tops with egg wash.

Bake for 18-25 minutes until golden brown. Allow to cool on the baking sheets for 5-10 minutes before transferring to a wire rack. Serve warm with salsa.