I left out the onion and added a little garlic powder and milk to the filling but otherwise made it just as the recipe said. It was really good. My husband, who can't stand sour cream, gobbled it up. I just didn't tell him the ingredients. I think this is my new favorite meal!
I made some changes (added dry Italian herbs to the sauteed onions, deglazed the pan with white wine, used 6 cups of milk instead of 3 1/2 for the sauce, played with amounts of cheese), but overall this was a great jumping off point for a delicious dish.
A little labor intensive but definetly worth the effort! Wonderful flavor. It's a keeper for sure!