Combine orange juice and cornstarch in a saucepan with no heat. Stir until cornstarch dissolves. Bring the mixture to a boil and boil for 1 minute, stirring constantly.
2 cups orange juice, 2 tablespoons cornstarch
Add orange marmalade and spicy brown mustard, reduce heat slightly, and stir until smooth. Transfer to a gravy boat and serve warm with ham.
⅓ cup orange marmalade, 1¼ teaspoons spicy brown mustard