I learned this one while on fishing trips to NW Ontario.
Get a "smallish" walleye filet weighing about 1/2-lb, and clean and skin it. Take a large sheet of tin foil; add a couple of strips of bacon on the foil; place the filet over the bacon and spice it w/salt and pepper; put a couple of thin slices of sweet onion and more than a couple of thinly sliced potatoes on top of the filet. Lift the corners of the foil to create a "bowl" and add a half-shot of white wine - nice stuff if you've got it - doesn't matter what it is but no sweet stuff. Fold the top and ends to seal it, and put a couple of knife holes in the top to release the steam.
Put this on the coals of your bbq for 12-min; or for about 15-min if you are putting it on the rack of a gas grill. Watch out when you open the package - the steam is hot!
Enjoy!