It's rather simple, I confess. I just cook (steam or steam-fry in a minimal amount of water) and then drain and food process until 'creamy.' I'm generally not a soupy type. A fork or spoon could literally stand up in my pureed vegetables--seriously! I was inspired to do this by a Food T.V show, "The Surreal Gourmet." It was an episode featuring "Brocco-mole" (i.e. pureed broccoli). The vegetables were presented on a painter's palatte in their colourful pureed/food processed form.
My favourites, I confess are leafy greens, i.e. baby spinach and swiss chard. Adding fresh herbs makes a huge difference.
Re: How to use these pureed vegetables? Sometimes I just eat them plain. They're great sauces, i.e. for rice/pasta/potatoes/noodles and fillings for such things as egg white omelettes/casseroles/veggie burgers/meatless loaves/mayo substitutes. They're wonderfully thick dressing/dips and bread spreads, I suppose or fillings for tortillas and stuffings for mushrooms. My favourite way to eat these things are just as a cold "salad." They're so flexible and adaptable and as I expand my menu a tad, I'm discovering how complimentary they can be.
I made a wicked broccoli puree last week--it was broccoli flowerets (frozen) and lots of fresh basil. I'm kind of hooked on making "faux-tatoes" (whipped cauliflower) as well--a favourite low-cal comfort food! I love pureed asparagus with herbs de provence and a bit of spinach and arugula or swiss chard.
www.fatfree.com has a lot of cool ideas that involve pureed veggies. One of my favourites combines green beans and spinach. You can give these purees the flavour/spices/"BAM!" or bang that suits your fancy.
It's rather like making hummus or baba ganush or whipped potatoes. Except less time consuming.