I followed this recipe:https://www.mygorgeousrecipes.com/potato-cheese-onion-pasty-recipe/
I would recommend 2 medium potatoes is enough for 4 large pasties.
I also added some hot and spicy cheese to one pasty.
Ingredients list I would recommend:
2 medium potatoes
1 large onion (fried gently for 10mins)
100g Mature cheddar cheese
1 TBSP Olive Oil
salt and pepper to taste
Baked in a preheated fan oven 200 for 20mins.