The phrase "packet mix" refers to a pre-packaged mixture of ingredients used to make a specific dish. It often contains all the necessary ingredients in measured proportions, saving time and effort in cooking or baking. Full definition
I eat my lunch — tuna packet mixed with mayo, crackers, cucumbers, and celery — while on the call. (refinery29.com)
Breakfast — pancakes made using a pancake packet mix and I added some mashed banana, an egg and some milk. (rachaelattard.com)
Original Cream of wheat instant packet mixed with 1/4 canned pumpkin, a packet of splenda, and of course pumpkin pie spice! (blog.naturalhealthyconcepts.com)