I made vege soup a lot . . . And yes, I know it's hot (Australia Day was 45deg, I still ate soup).
My dietician allowed low salt stock so I got chicken stock, added onion, celery, mushrooms, parsley, herbs and simmered. Take out the soggy bits and you have a guilt free base for 4 serves of soup.
Chop up your cup of veggies, microwave or stove top simmer and add as you go.
I would put in celery, broccolini stalks, zucchini and some red capsicum, maybe some mushroom and wilt spinach into cup as I served. The spinach doesn't amount for much cooked, and has some iron . . . And there is vitamin C in capsicum and broccoli (dietician would approve of combination)
It was crunchy texture, so I felt like I was eating something and filling (I didn't always want the third serve of opti, so my compromise was half bar for a/tea, half 'supper').
Good luck
Karyn :-)
PS. When you read thru the posts, you often see that some of the dietitians approve of having low-fat protein if starving. . . mine said I could have Thai beef salad the night before op (I had fish and veggies). Once you're thru the first few days of opti it's not too bad though.