Cook the chorizo in a large skillet. Reserve 2 Tablespoons of the drippings to cook with the potatoes, or drain completely and use canola oil.
While the chorizo is cooking, place the diced potatoes in a microwave-safe bowl and cook in the microwave for 3 minutes, stir and cook an additional 2 minutes.
Spoon the cooked chorizo into a bowl and place the potatoes and onions in the pan to cook with the drippings or 2 tablespoons of canola oil. Cook until the potatoes have browned.
Add the garlic, oregano and salt and mix to combine. Cook for another minute, then add the chorizo back into the pan and mix.
Line a baking pan with parchment paper.
Roll out the empanada dough or pie crust.
Cut out 2-3 inch circles from the dough. Put a large tablespoon of chorizo mixture in the middle.
Fold over and pinch to close well. Crimp the edges with a fork or your hands, or an empanada press.
Place them on the pan and refrigerate for 10 minutes.
Preheat the oven to 375°. Brush the empanadas with egg.
Place in the oven and bake for 12 to 17 minutes.
Check the crust on the tops and bottoms to ensure they are golden brown. Remove and serve with salsa or guacamole if desired.