I like to make the glaze while the pork chops are resting, or if someone else is grilling I will make it while the chops are on the grill
In a saucepan add the oil and garlic over low heat and lightly cook the garlic until it is warm and fragrant, about 3 mins. (make sure the garlic does not brown)
Add the thawed or semi thawed apple juice concentrate and warm thru.
Whisk in both mustards and the salt until they are well combined and emulsified. Increase the heat to medium, medium-low and bring the glaze to a hard simmer. (It will still be very thin at this point). Simmer for 2-3 minutes.
Mix together the cornstarch and water in a separate bowl. Stir until the cornstarch is dissolved in the water, make sure you get all thick cornstarch off the bottom of the bowl.
Turn the temp down to low and stir the cornstarch mixture into the apple juice/mustard mixture. Cook for another minute.
Pull the glaze off the heat. It will thicken as it sits, about 3 minutes. (If you want your glaze a little thicker put it back on low heat and add another 1 tsp cornstarch mixed with 1/2 tsp cold water)