In small *non-stick frying pan, add potatoes and corned beef. Fry over medium high heat for 10-12 minutes or until potatoes are done and lightly browned, stirring minimally. (*Time depends on how much you chopped the potatoes and onions.) Remove from heat.
Place pastry squares onto parchment paper-lined baking sheet. Spread each square with 1/2 teaspoons mustard off to one side. Top each with a mound of potato/corned beef mixture on top of mustard.
Wet two connecting sides, fold over and press closed to seal.
Pop into preheated oven and bake for 20 minutes.
Serve with warmed cheese sauce drizzled over.
*Optional garnish: snipped chives, but not needed. Optional only!
**Turnovers can also be brushed with an egg wash prior to baking, but not needed nor necessary. Only for presentation and does not effect this recipe.