I often substitute a pair of 2 ½ (or some combination) pork loins instead of the pork roast specified above. You can even by a bag of pork tenderloins and work with that.
Mix guava nectar, ginger root, ground ginger, brown sugar, and vinegar. Mix thoroughly to dissolve the brown sugar. Place marinade and pork in a ziploc bag and allow to sit overnight. If you can't wait overnight, you need at least 4 hours at room temperature for the marinade to soak in.
Preheat oven to 350°. I often use a crock pot for this recipe. If you are interested in an actual "glaze" you have to use the oven. If you are willing to accept the flavor without a glaze, you can use a slow cooker.
Brown pork in skillet then bake in preheated oven for 1 hour basting at least 4-5 times. In the slow cooker, place pork in bottom, cover with marinade and cook on low for 8 hours. Spooning the marinade over the pork in the slow cooker is not required, but adds flavor.
Once pork is cooked, use remaining marinade to make a sauce. Bring marinade to a boil in skillet, add cornstarch until it begins to thicken (quantity of cornstarch varies depending on how much marinade you have left).
Slice roast or loins and serve slices with a drizzling of the sauce. Side dishes such as asparagus and green beans go especially well with this dish.