1x-large vidalia onion sliced into small wedges [or 2 medium]
salt & black pepper
1Tbspred wine vinegar
3finely chopped green onions
2 1/2Tbspall purpose flour
1 1/2cupswhole milk
2cupsshredded muenster cheesedivided
2Tbspchopped Italian parsleydivided
For the crumb topping:
1 1/2cupsfresh bread crumbs
1Tbspchopped Italian parsley
Preheat the oven to 350°F. Butter the bottom and sides of a 1 1/2 quart baking dish, then set aside.
In a heavy saucepan, saute the mushrooms and sliced onions in a couple of drizzles of olive olive until the mushrooms are golden and they've released their liquid. Season with salt and pepper to taste. This step will take around 12 minutes.
To the mushrooms, add the minced garlic, fresh thyme, 3 tablespoons of butter, 1 tablespoon of red wine vinegar and 3 chopped green onions.
Continue to saute over medium heat for 2-3 minutes until the garlic has cooked and the butter has melted.
Add 2 1/2 tablespoons of flour and cook for 1 minute until the flour has coated all of the ingredients.
Increase the heat to medium high and add 1 1/2 cups of milk. Cook until the mixture is bubbly and has begun to thicken. Around 2-3 minutes.
Add 1 1/2 cups of shredded muenster cheese and 1 tablespoon of chopped Italian parsley to the creamy mushrooms. Cook just until the cheese melts.
To make the crumb topping: In a small bowl melt 1 tablespoon of butter in the microwave. Toss the breadcrumbs, chopped Italian parsley and garlic salt with the melted butter to make the crumb topping.
Pour the mushrooms into the buttered baking dish and sprinkle the remaining shredded muenster cheese on top.
Spread the buttered crumbs evenly over the cheese.
Place into the oven and bake for 25-30 minutes until the topping is golden and the edges are bubbly.
Allow the gratin to sit on the counter for 5-10 minutes before serving to allow the sauce to thicken.
For this dish I purposely chose muenster cheese for it's saltiness. Gruyere cheese also works beautifully in this dish!