Start by stripping your vegetable
to as pure a form as possible. While, in some cases, you can discard skins or seeds later, I like to do as much of the prep work in advance so I don’t have to strain or handle a hot puree.
In this case, I peeled the carrots and trimmed off the ends.
Chop the vegetables into small, even pieces
They'll cook at the same rate, and will be easier for your blender to attack later.
Choose your cooking method
For most veggies, you have the choice to sautee, roast, steam or boil. A good guideline: Cook them the way you like to eat them. You would never boil an eggplant or steam an onion, so follow your instinct.
I prefer boiling whenever possible, because it's quick and kills two birds with one stone: if you flavor the cooking liquid, you can later use it for the blending.
My favorite formula is one part cream to three parts chicken stock. I love the balance of flavor and creaminess it gives.
Add enough liquid
to just cover the vegetables.
If baking or sauteeing instead, try not to use excessive amounts of fat, which could make for an oily emulsion if you plan to add liquid or cream later.
Season as you wish
(Bay leaf and salt are my usual go-tos) Remember to wrap in cheesecloth any herbs or flavorings that you don’t want to later see in the puree, or grind them in a spice grinder. You can also save the seasoning till the end.
Here I brought the carrots to a simmer and cooked them fully, until a fork passed through with no resistance.
Drain the vegetables, reserving the cooking liquid
and removing any large spices you don't want to puree. Add a glob (yes, that's a professional term) of butter if using, and the veggies to a blender.
Start ladling the warm cooking liquid into the blender. (If you used water here or plain stock, have some extra liquid and heavy cream warm on the stove for this step.) Add enough cream and liquid to cover the vegetables by about half. You will most likely need more, but it’s easier to add liquid than take it away.
If you have a Vita Prep or other high-powered blender, yay for you—whip that bad boy out, cover it carefully, and turn the speed from low to high as the puree breaks down.
Start the blender off slow, then increase the speed as it gets going, adding more liquid as needed until it reaches the desired consistency.
Test it by spooning a bit onto a plate. I like mine thin enough to run a bit, but not so thin that it doesn’t hold shape—sort of like a melty, soft-serve ice cream.
If you were working with a tough or fibrous veggie, or one with skins or shells like tomatoes or peas, this would be the point at which to run the puree through a medium-mesh sieve to smooth.
Adjust seasonings. Stir in any additional cream or liquid. Garnish, Serve!