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1
Preheat oven to 400F.
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2
Combine both broths, Port and garlic in heavy small saucepan.
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3
Boil until sauce is reduced to 3/4 cup, about 20 minutes.
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4
Set aside.
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5
Meanwhile, melt 2 tablespoons butter in large skillet over medium-high heat.
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6
Add shallots and saute until translucent, about 1 minute.
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7
Add mushrooms and leek and saute until tender, about 6 minutes.
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8
Stir in cream.
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9
Cook mixture until vegetables are soft and most of cream is absorbed, about 5 minutes.
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10
Cool.
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11
Insert handle of wooden spoon lengthwise into cut end of each tenderloin, forming 1/2- to 3/4-inch-diameter hole.
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12
Transfer mushroom mixture to pastry bag fitted with large plain tip.
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13
Force mixture into center of each tenderloin, filling hole completely.
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14
Rub tenderloins with marjoram.
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15
Sprinkle with salt and pepper.
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16
Heat oil in large ovenproof skillet over high heat.
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17
Add tenderloins to skillet and cook until brown on all sides, about 6 minutes total.
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18
Transfer skillet to oven.
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19
Roast tenderloins until cooked through, about 8 minutes.
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20
Remove skillet from oven.
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21
Transfer tenderloins to platter; tent with foil to keep warm.
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22
Return skillet to stove.
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23
Whisk in sauce.
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24
Bring to boil, scraping up any browned bits.
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25
Remove from heat.
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26
Whisk in 4 tablespoons butter.
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27
Cut tenderloins crosswise into slices.
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28
Spoon Celery Root Mashed Potatoes onto plates.
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29
Arrange tenderloin slices around mashed potatoes.
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30
Drizzle sauce over and serve.
