How do I create linked nodes without user intervention?
A solution that doesn't go deep into the code is to use the Prepopulate module.
It enables you to prepopulate form fields through the link to the form page:

http://www.example.com/node/add/recipe?edit[field_entity_reference][widget][0][target_id]=123


You'll probably want to construct the links automatically, it can be done with Views. You create a Block Display that contructs the link using the Food information it's been placed on, through a contextual filter. When the Block is placed on Food pages the link leads to new recipe form that has the food where you just left from already filled in.
You can find more info about how to construct the link with the help of Views in this answer: Add Prepopulate links to Node pages part of the answer.