Heat oven to 200C/fan 180C/gas 6. Season the pork and
rub rosemary over. Heat 1 tbsp oil in an ovenproof frying
pan. Cook the pork for about 10 mins until browned all over,
then set the pan aside. In a roasting tin, toss the chicory
and remaining oil. Place in oven, put the pork in the frying
pan on the shelf below and cook for 15 mins. Remove the
pork to a plate, cover with foil and leave for 5 mins.
Pour away any excess oil from the frying pan, then heat
it on the hob, tip in the membrillo, stock and wine, and
swirl around, scraping up any meat juices. When the
membrillo has melted and the sauce is glossy and warm,
slice the tenderloin and serve alongside with the chicory.