First, prepare the mash by defrosting it.
Break the egg and beat it in a bowl.
Lay out your 10 tortillas and brush the face-up side with your egg.
Meanwhile, fry up your onions in a pan over a medium heat until they start to turn translucent.
Mix your grated cheese into the mash, and add the onions. Mix thoroughly with salt and pepper, tasting as you go, until it reaches the right level for you.
Spoon out enough of the mixture to fill each tortilla and place it roughly in the middle or towards the bottom half of each.
Fold your tortillas over and gently push down - if any of the mixture squishes out, you can use a fork or spoon to skim it off the edge.
Apply egg wash to the outside of the tortillas. You can either just do the top and let it bake, or do both sides and turn halfway through cooking. As this isn't real pastry, you don't have to worry as much about cooking it correctly!
Use a fork to gently crimp the edges of each tortilla - this also helps it to stay closed. Add a little extra egg mixture to seal the edges if you feel it is needed.
Put into the oven at 180C fan/200C for at least 15 minutes. From there, keep an eye on the pasties until they reach the level of browning that you prefer - just don't let them burn!
We used Old El Paso corn mini tortillas to make this recipe, but other mini tortillas would work just as well - whether they are round or oval.