Place leeks in the bottom of a roasting pan and cover with the rack of pork. Generously season with salt and pepper and pour in 500 ml (2 cups) water. Sear in oven for 30 minutes.
Mix vinegar and syrup and pour over the pork.
Remove from oven and reduce temperature to 350oF (180oC).
Pour the vinegar/syrup mixture over the pork and add the thyme.
Cover and return to oven for 1 hour, remove the lid and continue cooking for 30 minutes more or until temperature reaches 160oF (70oC) on meat thermometer.
Remove pork from oven, pour cooking juices into a sauce pan. Cover rack of pork and let stand for 5 to 10 minutes.
Dilute cornstarch in cream and add to cooking juices, stirring with a whisk. Bring to a boil, allowing to thicken.
Cut between bones and serve one rib per person with sauce and leeks.
