Wash the orange and the lemon well. Slice the fruit and sliced ginger and place into a medium pot along with 5 cups of water. Bring the pot to a boil, and then simmer for 30 minutes. Drain water with a sieve, press the fruit into the sieve, you want to get all of the water released. Place water into a pot and add 1 cup sugar, 1/2 cup vinegar, and 1 cup ketchup mix until well blended with a whisk. Heat the sauce over medium high heat.
Combine 3 tablespoons corn starch and 3 tablespoons water in a small bowl. Slowly stream the liquid into the sauce stirring constantly. The sauce will thicken. When the sauce thickens remove from heat. Store unused sauce in an air tight container.