To make Chicken Pan Gravy. If your roasting pan can go on the top burners of your oven put the roasting pan with the leftover vegetable rack on your burners on medium high heat to get it simmering. Add 2 cups of water, a pinch of salt and a pinch of pepper. Mash up all your veggies to extract as much of the flavour as possible while simmering. Stir well to pick up any brown bits on the bottom and mash until it's good and pureed. Make a slurry by whisking together 2 tbsp cornstarch + 1/4 cup chicken stock. Mix in to gravy and one more cup of chicken stock stirring for about 1 minute. Remove from heat and strain your vegetable puree. Pour back into pot to keep warm. When ready to serve pour into a gravy boat.