Thought purées were for babies?
Then this could change your mind. It's silky smooth texture has a very pleasant mouth-feel, and the flavour is delicate and creamy. You could get all 'chef-y' and put a generous swirl, or a swoosh of cauliflower purée across a plate (maybe even with a scattering of my crunchy Sauteed Cauliflower with Cumin and Almonds for a contrast of textures).
This is delicious with the above (Octopus with Peppers and Chorizo) with added garlic, and also makes a delicious change in a little curved deep swipe on the side of your sunday lunch, with a little of the gravy/jus creeping into the groove and a few peas scattered over it, or with a starter of plump, juicy scallops as a base for each scallop, with either some crisp pancetta, or diced crispy chorizo, or even a few small slices of pan-fried black pudding and some curling tendrils of pea shoots scattered around. It freezes exceptionally well, and is easy to re-heat and serve - tastes just like the day it was made!
This quantity will make more than enough for eight portions (56 calories each) to serve with a starter, or a garnish / side to a main meal (I don't think you'd want too much of it by itself, however delicious it is) with other vegetables, and you can put any you don't use into the freezer for the next time (a re-sealable sandwich bag is great for this, squeeze out the air and it will keep for months, and you can just break off what you want).
300g cauliflower florets (you can include stalk, peel it if tough on the outside) 
300ml milk (semi-skimmed - or substitute light coconut milk for Paleo) 
25g butter 
(Optional 4 cloves of garlic, to make a cauliflower and garlic puree )
Cut the cauliflower florets into smaller pieces and put into a pan (with the garlic if using), cover with the milk, add a pinch of salt and bring to the boil, then simmer for about ten minutes or so or until completely tender (if it's not tender, you'll get a grainy puree).
Get a jug or container to reserve the hot milk in, and carefully drain the cauliflower over it. Add the cauliflower and butter with a little of the hot milk to a food blender or processor (thermomix is perfect for this) and blitz. After this, add a little milk at a time until it is the consistency that you want (you're unlikely to need all of the milk, you may even want to make a creamy cauliflower 'mash' rather than a purée). Once you've reached that stage, try a little and add more salt to taste if necessary.
I don't add pepper to this, because I don't particularly like white pepper, and I don't add black pepper for aesthetic reasons, as it will generally be elsewhere anyway, but season it to your own preferences, depending on what you're doing with it.
If you're counting calories, you can reduce or skip the butter if you want to cut them down, and obviously if you don't use all of the milk, you can deduct what you don't use for the overall calorie content.