It's a rather complex recipe. 

1) Put cheese (your choice) on parchment paper in little piles.
2) Put pepperoni slice on cheese.
3) Bake at 400f for 10 minutes or desired crispiness.

Looks like a great topping on a burger

Do you serve them at room temperature?

Do you serve them at room temperature?

Yes, need to cool down for the cheese to crisp up.

My wife will grate Parmesan and bake into chips, if you like good Parmesan they are fantastic.
Never thought about pepperoni, bet they are great.

This was a Mexican blend cheese.
Was going to try Mozzarella, but it was frozen.
Have some frozen Parmesan also, will try that too.

Those are probably great.

have not done these in a long time. Never put pepperoni on them when I did, but good idea.

If you have good American not the Kraft plastic stuff. You can quarter it and  make nice little crackers from it.

Something else that is good, and works great in a cast iron skillet, is a thick 3/8 to 1/2 slice of cheese. I have tried many different ones. get you skillet hot lay the slice  in and it will brown and start to melt cook some of the oil out of it, when it gets to your liking on how brown flip it over, and do the other side until you like it. then take it out salt and pepper. crisp in the outside warm and soft inside. Some cheese is messier than others. Now you have oil for your eggs.