The wonders of frozen pastry

I have been doing a lot of party catering recently, and one of my favorite standby, easy peasy treats, is to buy small sheets of frozen puff pastry and make things like this;

Cherry Tomato and Dijon Tarts 

So my last trip to cash and carry taught me one very valuable lesson. Don't go shopping without your glasses, or you could end up with these instead;

As you can see, the sheets are just a wee bit bigger.
Of course, you could just cut them into smaller squares, or you could alter your project, which is what I did.

 I smeared a generous layer of Dijon Mustard over the bottom pastry sheet, together with a layer of sliced onions, and then added ham slices cut off the bone.

On top of that, I added a layer of Feta, just because that's what was in the fridge, but you could use any cheese really.

You could add any herbs you like at this point, but it doesn't really need it. Coarse pepper is always nice in these dishes, so go ahead and sprinkle.
Cover with a second layer of pastry, prick, crimp and egg wash, (sounds like a firm of solicitors) and pop into an oven for 30 minutes or so, at 350 degrees.

 Remove when nicely golden brown and cut into slices when it is cool. I did take a photo of the sliced pie, but before I got round to opening it and discovering it was out of focus, the pie had all gone.
It was SOOOO good.