I like to use Porcini mushrooms and French haricots verts for their intense flavor and firmer texture; but you can certainly use white button mushrooms and any variety of string beans available at your local market.  If you are short on time, skip making Panko onion rings and use store-bought French’s® French Fried Onions.

Thinly sliced onion rings are tossed with Japanese panko bread crumbs and baked until golden brown.

Trimmed green beans are blanched then tossed in a homemade mushroom sauce along with half of the onion rings.

Everything is then poured into a casserole dish a oven-baked until bubbly.

Remaining onion rings are added on top and the green bean casserole is baked for another 15 minutes or so until crispy.

HARICOTS-VERTS CASSEROLE WITH PORCINI MUSHROOM AND ONION RINGS

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4 medium brown onions, thinly sliced
1/2 cup all-purpose flour
6 tablespoons Japanese Panko bread crumbs
1 teaspoon kosher salt
Nonstick cooking spray

1 tablespoon plus 2 teaspoons kosher salt, divided
32 oz fresh haricots verts, ends trimmed
4 tablespoons unsalted butter
24 oz Porcini mushrooms, sliced
1-to-1 1/4 teaspoons freshly ground black pepper
3-to-4 cloves garlic, minced
1/4-to-1/2 teaspoon freshly ground nutmeg
4 tablespoons all-purpose flour
1 cup chicken broth
1 cup whole milk
2 cups half-and-half

Preheat oven to 475F.

Combine onions, flour, panko crumbs and salt in a mixing bowl and toss.  Coat a sheet pan with nonstick cooking spray and evenly spread onions on pan.  Place on the middle rack in the oven and bake until golden brown; about 30 minutes.  Toss two to three times during cooking.  Once done, remove from oven and set aside until ready to use.  Reduce oven temperature to 400F.

Meanwhile, prepare beans.  Bring a gallon of water and one tablespoon salt to a boil in a saucepan.  Add beans and blanch for 5-to-10 minutes until almost tender.  Drain and immediately plunge into a bowl of ice water; drain and set aside.

Melt butter in a skillet set over medium-high heat.  Add mushrooms, 2 teaspoons salt, and pepper and cook, stirring occasionally, until mushrooms begin to give up some of their liquid; approximately 4 to 5 minutes.  Add garlic and nutmeg and continue to cook for another 1 to 2 minutes.  Sprinkle flour over mixture and stir to combine.  Cook for a minute.  Add broth and simmer for another minute.  Decrease heat to medium-low and add milk and half-and-half.  Cook until mixture thickens, stirring occasionally; approximately 6 to 8 minutes.

Remove from heat and stir in half of the onions and all of the green beans.  Pour into a casserole dish and bake in the oven until bubbly, for about 30 minutes; stirring occasionally.  Top with remaining onions and bake another 15 minutes until onions are crispy. Remove and serve immediately.

recipe adapted from Alton Brown {Good Eats, 2007}; via the Food Network