Go to a blank day in the future, like tomorrow, and enter all the individual ingredients. Then divide the total calories, grams of protein, fats, and carbs by the number of servings. Then create a new custom food called Chicken Stir Fry and enter in the values for one serving and save it. You'll have Chicken Stir Fry listed in your custom foods for the future!
(Don't forget to delete everything from tomorrow's page when you're done!)
PS - when's dinner? Sounds good!