The classic, humble gratin with its thick, crispy bubbling crust, has been defined and redefined over the years. Whether its base is potatoes or eggplant, fish or shellfish, pasta or meat, whether it is a main course or a dessert, the gratin seems to find its way to our dinner tables.
The difference between au gratin and gratin is that potatoes au gratin are a side dish made with thinly-sliced layers of cheesy potatoes. ‘Gratin’ is the culinary technique of baking or broiling an ingredient topped with grated cheese and breadcrumbs to create a crispy crust.
The word gratin derives from the French word grater, meaning ‘to grate‘. You would think that gratin refers to grated cheese, but this is not what the word originally referred to. Instead, it meant something more like ‘scrapings’. This referred to the browned, crusty material that forms on the bottoms and perhaps to the act of scraping loose these crusty bits and stirring them back into the dish during cooking. It now tends to refer to the browned crust that forms on the top of a baked dish, whether this crust forms by itself or is speeded up by placing the dish under a broiler.
Since Brion & I are both mushroom lovers, portobello & potato gratin certainly works for us.

Servings |
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- 4 Portobello mushrooms, sliced horizontally
- 142 gm muenster cheese, shredded
- 1/3 cup breadcrumbs
- 2 Tbsp parsley, chopped
- 1 clove garlic, minced
- salt & pepper to taste
- 3 Tbsp water
- 907 gm potatoes, cooked & mashed
- 2 green onions, sliced
Ingredients
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- Cook potatoes & mash, adding enough milk just to make creamy. In an oblong casserole dish, spread some potatoes on the bottom & up the sides.
- Preheat oven to 400 F.
- Clean & slice Portobello mushrooms into about 3 slices each. Toss cheese, breadcrumbs, parsley, garlic, salt & pepper. In the center of the casserole dish, layer the Portobello rounds & cheese mixture making 3 layers.
- Drizzle the mushrooms with 3 Tbsp water, cover with foil & bake 35 minutes. Uncover & bake 8 minutes more. Remove from oven & sprinkle with sliced green onions. Serve.