Remember when I made rough puff pastry a million years ago and promised that I'd make a post about fillings?
This is that post, and I can only apologise.
With pastry, I find a good general rule for making small-ish filled pastries is to use an equal weigh of filling to the weight of pastry. So, weigh your pastry when you're getting ready to fill it. Say it weighs 1kg. Then if you want to fill your pastries with steak and kidney (though why you'd want to do that is beyond me), you would use 500g of each, to make a total of 1kg.
My first filling is cheese, onion and potato. I used 1/3 of the weight of each, to make the total weight of my pastry. Preparation was simple. I cut up the potatoes into cubes of about 1cm (the size you choose would depend on the size you want your finished pastries to be) and then boiled them for about five minutes. They were just starting to get soft but nowhere near the falling-apart stage. Then I chopped the onions up into pieces of a similar size, and fried them until they were nice and soft but before they started to brown. And finally, I divided the cheese roughly in half, and grated one half, then chopped the rest into 1cm cubes again. This was just for variation of texture, and you could really do the size and shape however you like.
Once all the fillings were ready, I just mixed them together a bit and then filled the pastries. First I rolled out the pastry, then cut it into rectangles (the shape would obviously depend on the shape you want the pastries to be). Then just put some of the filling on one half of the pastry, and fold the other half over. I brushed a bit of milk around the edges to help the pastry seal, but this isn't always necessary.
To finish them off, I pressed a fork around the edges and scored the tops with a sharp knife. These make them look nicer but also aren't really vital. Then bake, at 180C until they look done. It's pretty easy to tell, because the pastry will be deliciously puffy and golden. Enjoy!