Mix cornstarch into 1 tsp cold water, stirring until dissolved and set aside.
Add broth and vegetables to a large frying pan and bring to a boil. Reduce heat and add maple, apple cider vinegar, soy sauce, juice, garlic pepper and agave if using. Cook for five minutes or until vegetables are cooked but still slightly crisp.
Add cornstarch mixture and stir to combine. turn theh eat to high and wait for the sauce to thicken, but keep a watchful eye! Once the mixture is thick like a glaze, remove from heat.