Preheat the oven to 400°F.
Place the pastry shells on a baking sheet and bake until golden brown, 20 to 25 minutes. Remove from the oven, and, with the tip of a thin sharp knife, carefully cut out the tops from each pastry; discard the moist insides. Let the pastry shells cool.
Heat the olive oil in a large skillet over medium-high heat. Add the mushrooms, salt, and pepper. Cook, stirring occasionally, until the mushrooms soften, about 4 minutes. Add the shrimp, green onions, shallots, and garlic and stir-fry for 1 minute. Remove the pan from the heat and carefully add the Cognac. Have a large lid nearby. Return the pan to the heat, and very carefully ignite the brandy. Once the flames go out (you may need to cover with the lid to extinguish if the flames leap too dramatically), add the cream, mustard, and parsley and stir well. Reduce the heat to medium-low and simmer for 2 minutes.
To serve, place a pastry shell on each of six plates. Spoon the shrimp mixture into each shell. Serve immediately.
Yield: 6 servings