To create a dish for theoretical calculations such as buffets and set menus please follow the steps below.
Click the Admin Cogs along the top bar.
Click Menus, Dishes and Recipes, then Manage Dishes.
Click Build New Dish, complete the details of the dish as required and ensure the check box Use for theoretical calculations only is on.
Click Create, then populate the Ingredients tab with all the ingredients/dishes/recipes that make up the buffet/set menu.
Using the Menu Prices tab assign the dish to the menu using the Add Menu Price button.