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1
Heat oven to 375 degrees.
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2
Use 1 tablespoon butter to grease a 2- to 2 1/2-quart baking dish or gratin.
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3
Bring a large pot of water to a boil, salt generously and add green beans.
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4
Boil for 5 minutes and transfer to a bowl of cold water.
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5
Drain on a kitchen towel.
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6
Heat a large, heavy skillet over medium heat and add bacon.
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7
Cook until crispy, about 10 to 12 minutes.
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8
Remove to paper towels and let cool.
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9
Discard all but 2 tablespoons of bacon grease in pan and return to heat.
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10
Add shallots and cook, stirring, until they begin to soften, 2 to 3 minutes.
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11
Add mushrooms and turn heat up slightly.
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12
Cook, stirring and scraping the bottom of pan, until mushrooms begin to sweat.
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13
Add salt to taste and cook until tender, about 5 minutes.
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14
Remove from heat.
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15
In a large bowl whisk together creme fraiche and cream.
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16
Stir in Gruyere.
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17
Add green beans, mushrooms and shallots, and marjoram or thyme.
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18
Crumble in bacon.
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19
Add salt and pepper to taste and stir everything together until beans are well coated.
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20
Transfer to baking dish.
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21
Melt remaining butter and toss with bread crumbs.
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22
Sprinkle evenly over top of casserole.
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23
Bake 30 minutes, until bread crumbs are golden brown and casserole is bubbling.
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24
Remove from heat, let sit until bubbles subside, and serve.
