how to create gratin with _thin_ cheese skin Several years ago I knew a place where they served ragout fin au gratin in small bowls with a very thin cheese skin. 

I'd like to create these myself. I tried several approaches, mostly by putting finely grinded Parmesan into milk or cream, sometimes combined with egg, (with nice results some times), but the resulting cheese skin is not as desired. The problem I'm having is that either the mixture is too runny and flows to the rim of the bowl or it is too thick and will result in a (tasty) skin which is, too thick however. Any ideas what I could try? Different kind of cheese maybe? Try again until I find the correct mixture?
I would think all of the above will give tasty results, the point about the use of a professional broiler or salamander is possibly the real clue for cheese to crisp it needs heat, the rest of the dish probably does not.

There are a few tricks to try, 

1 use any of the above mixes but get yourself a blow lamp from the DIY store or garage, not a silly little overly priced armature cook shop one, and use it to flame the tops just before serving(warn guests of the temperature before they burn their mouths) Effectively same as a good crème brulee. 

2 make parmigiana disks grate parmigiana very finely on to a silicon tray or baking sheet oven roast until crispy or use grill if you have a hot broiler. let them cool on a rack place them on top at the end of the cooking - Combine with the blow lamp to colour and heat as a professional touch.

3 the lazy way add a dash of butter to the tops during the baking to colour the cheese mixture.