Cldy,
Deffinately defrost first.
My basic recipe is to brush the base of the PC with oil and then add a large chopped up onion and saute this for a couple of minutes. I think this adds to the flavour of the whole thing. Add the whole chicken. I mix a bit of chicken stock into 1 pint of hot water and because its my favourite flavour I add a tsp of tarragon. I cook mine on high pressure for 30 mins. Wait till its warm then strip the chicken of it's skin and leave the liquid to go cold so that the fat will solidyfy on the surface to easily scrape off what is now a rich jelly stock.