Place apricots and rosemary in a saucepan and cover with water by 2 inches. Bring to a boil, then reduce heat and simmer for 25 minutes. Apricots should be soft and plump.

Let cool in any remaining water for 30 minutes. Remove and discard rosemary, drain apricots and add to a food processor with the remaining mousse ingredients and process until smooth. Place in the refrigerator while you begin the assembly.

Place flour into a large shallow bowl. Add salt and stir to mix. Cut in butter using a pastry blender or pinch it with your fingertips.

Add 6 tablespoons water and mix into the flour mixture with a fork.

Add an additional tablespoon of water, if needed, in order to form a smooth dough.

Shape into a ball and chill for 30 minutes.

Melt 2 tablespoons butter in a small saucepan and add the shallot, cooking until soft.

Add the porcini powder and sauté 30 seconds.

Add the demiglace concentrate and the white wine and whisk until smooth.

Strain into another small saucepan and add the chicken stock; simmer until thickened. Set aside.

Season pork well with salt and pepper and brown on all sides in butter over medium-high heat. Transfer to a plate and set aside to cool.

Preheat oven to 400°F/200°C.

Roll out one pastry sheet to a 16-inch square and divide it into four 8-inch square pieces. Trim pastry corners.

Place 2 tablespoons of apricot mousse in the center of each pastry quarter. Top with a piece of cooled pork and fold up sides and ends to make little packages, sealing the corners well. Place seam-side down on a baking sheet and brush tops and sides with egg wash.

Bake 15 minutes. Turn off the oven and start the broiler; broil until then crusts are golden.

Reheat the sauce, thinning a bit with stock or water if too thick.

Place a package on each of 4 warmed plates, and pool sauce around them. Serve each with a sprig of rosemary.