I have made a few dishes with passata and found that the sauce I made with it was nice but a little bit watery.
After looking for some tips I found one which works really well, Smash, which is free (unless it is the buttery one which has syns).
All you have to do is sprinkle in enough and keep stirring until your sauce is the desired thickness. I was worried when I first did this that my sauce would taste of potatoes but it didn’t at all.
This is much better than using cornflour or flour — which has syns, or my old favourite roux which is made by cooking butter and flour together, super tasty but full of syns!