A "farro mixture" refers to a combination of farro, which is a type of grain, with other ingredients. It means that farro has been cooked or mixed with different foods to create a dish or meal. Full definition
For Sunday prep, omit the arugula and make enough farro mixture for the week. (cookinglight.com)
Pour remaining oil into pan and stir in onions; continue cooking for 4 - 6 minutes until lightly browned, then add to farro mixture. (villageharvestrice.com)