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1
Preheat an oven to 325u00b0F.
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2
Season the beef with salt and pepper. In a 3 1/2-quart wide Dutch oven over medium-high heat, warm the olive oil. Working in batches, brown the beef on all sides, 8 to 10 minutes per batch. Transfer to a bowl.
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3
Reduce the heat to medium. Add the prosciutto and cook, stirring occasionally, until crisp, 6 to 8 minutes. Add to the bowl with the beef. Increase the heat to medium-high, add the mushrooms and cook, stirring occasionally, until tender, about 8 minutes. Add to the bowl with the beef.
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4
Pour off the excess fat in the pot. Return the pot to medium heat and melt the butter. Stir in the flour and cook, stirring constantly, 2 to 3 minutes. Whisk in the wine and demi-glace and cook for 1 minute. Slowly whisk in the stock and bring to a simmer. Add the thyme, bay leaf, pearl onions, beef, prosciutto and mushrooms. Lightly season with salt and pepper. Cover the pot, transfer to the oven and cook until the beef is fork-tender, 2 to 2 1/2 hours. Discard the bay leaf and spoon the excess fat off the cooking liquid. Stir in the parsley.
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5
Increase the oven temperature to 400u00b0F.
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6
Place the puff pastry sheet on a lightly floured work surface. Using a sharp knife, score the pastry with diagonal lines about 2 inches apart, forming a diamond pattern. Brush the edge of the pot with water, then brush the pastry with the egg mixture. Place the pastry, egg wash side up, over the pot and press the edges to seal. Trim the overhanging pastry to 1 inch.
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7
Transfer the pot to the oven and bake until the pastry is puffed and golden brown, 20 to 25 minutes. Let rest for 10 minutes before serving. Serves 6 to 8.
