You can assign multiple ingredients to a product, and a single ingredient can be assigned to multiple products. 

When a new ingredient is assigned to a product that was already sold, the Ingredient Report includes the new ingredient in all previous sales. For example, if you’ve already sold ten burgers and then assign a tomato ingredient to the burger, the Ingredient Report includes the tomato as part of the previous ten sales.

1. In Restaurant Manager, on the Products page click the Products tab.
2. Click the category that contains the product.
3. Click the product.
4. In the Advanced options click Choose Ingredients.
5. Select the ingredient from the list.
6. Enter the unit quantity for the ingredient and click +.