For a start you might gogle 'Word includetext' which would pull up many references including
https://wordmvp.com/FAQs/TblsFldsFms...textfields.htm
I've attached your sample file where I've modified the text to use an include text field for the first three sets of ingredients.
When saving the ingredients as a seperate file make sure you delete the final paragraph markers otherwise this will appear in the imported text.
When you insert the field your usage means that you want to make sure that the 'Preserve formatting during updates' checkbox is unchecked.
The field is inserted using
Insert.Quick Parts.Field....
Scroll down to find Include Text and select it
Add the file path/name
Uncheck 'Preserve foprmatting during updates'
Click OK