I never knew that 'rule', and I have always done it!
I use frozen peas, broccoli and green beans. I always did with DD aswell and we have never had a problem.
Jack has just been through a spoon refusal phase (mixed with some teething and a tummy bug) and basically would only eat finger food, so for a good few weeks I was so stressed out with his feeding.
Basically he lived on:
carrot sticks (cooked, frozen in tubs, and thawed)
swede cubes (as above)
peas
potato cubes (same)
cheese spread on wholemeal bread (cut into small squares)
pear slices (tinned)
banana slices
cheese cubes
toast
breadsticks
cheerios
Now I am relieved to say he is over his 'your not allowed to feed me with that spoon' phase. So I am making pretty much the same food as he used to eat when all was good, but now I mash instead of puree.
I either cook the veg/meat or whatever and freeze it whole, in storage tubs.(Or if we run out of tubs, we have used freezer safe tin foil) then you just need to leave to defrost over night and warm and mash it when needed.
Or I will cook and mash it, then freeze it in a small tub. You can buy those ones that are perfect for fitting 1 meals worth of mashed food into-but you need quite a lot if you want to store it in bulk
we just seem to have accumulated a cupboard full over time.
I read a post on here the other day which was quite useful, heres the link (I hope!)
https://babywhispererforums.com/index.php?topic=57557.0Wow, that ended up being quite long-sorry! Just rambled on a bit then!
Hope that helps you out.
Love