Preheat oven to 375 degrees F. Line a baking sheet with parchment paper.
Brown and break up the ground beef. Drain any grease.
Add the taco seasoning and water. Bring to a simmer, reduce heat and cook until thickened.
Stir in the corn and black beans then let the mixture cool slightly.
Place a biscuit on a clean work surface sprinkled with flour. Use a rolling pin to flatten the biscuit.
Add a spoonful of the taco mixture and a pinch of Mexican cheese to one side of the flattened biscuit.
Fold over the biscuit and use a fork to seal the edges closed. Brush the top of the biscuit with egg wash. Repeat with the remaining 9 biscuits.
Bake for 10-14 minutes, until each pie is golden.