Stuff each hen with 6 prunes and 4 apricots, interspersing the lemon slices among the dried fruits.
Truss the hens and set aside.
In the fat remaining in the cooker, saute the shallots, celery and ginger for 2 minutes.
Stir in the stock and salt; scrape up any browned bits that are sticking to the bottom of the pan.
Place the hens side by side in the sauce.
(You may need to put one hen on its side) Place the sweet potatoes on top Lock the lid in place and over high heat bring to high pressure.
Adjust the heat to maintain high pressure and cook for 10 minutes.
Quick release the pressure and check for doness by inserting a knife into the drumstick joint; if the meat is still pink, lock the lide back in place and return to high pressure, and cook for another minute or two.
Transfer the hens to a platter; remove the trussing.
Reserve in a warm place.
Add the orange zest and Grand Marnier and boil the sauce over high heat until the alcohol burns off and the sauce is reduced slightly, about 3-4 minutes.
Serve in a sauce boat, or pour over the stuffed hens.