Some purists would say that making crème fraîche with pasteurized cream is a waste of time, that there is no substitute for the real, raw stuff found in France.
They are half right. Crème fraîche from unpasteurized cream is a revelation, and if you are lucky enough to live someplace where you can get it, you should stop reading this and go buy un petit pot immediately. I know I would.
If you don’t live in France, you can make a more than adequate version of crème fraîche by adding a little buttermilk, which contains benign bacteria, to heavy cream and letting it ferment at room temperature for 12-24 hours. The result is a thick, silky, slightly soured cream that adds tang and richness to myriad dishes, sweet and savory. I love it.
You could buy it, I suppose. It’s available at specialty shops and, increasingly, at mainstream groceries. But a half pint typically costs twice as much as the same volume of heavy cream. Twice as much! The way I see it, you’ll end up ahead of the game even if you don’t use up all of the leftover buttermilk before it goes bad. If créme fraîche is something you like to have in the fridge at all times, you can use a dollop of the batch that’s winding down as the starter for the next round; no need to buy more buttermilk.
Try to find cream that is just “pasteurized,” not “ultra-pasteurized”. It will have more flavor. And read the label on the buttermilk carefully, because some brands actually have salt in them, which you do not want. Many people say to use a glass jar to ferment the cream but I’m not sure why you couldn’t use a plastic container, so long as it is perfectly clean and odor-free. (If anyone out there knows why not, please tell me.)
Crème fraîche is higher in fat than American sour cream, has a smoother, silkier texture, and won’t curdle when you stir it into something hot. On the savory side, I love it in mashed potatoes, in my scrambled eggs, or as a garnish for soups hot and cold. Try tossing some cooked spinach, well drained, with a tablespoon or two of crème fraîche and plenty of freshly ground black pepper. In gratins or pastas that call for cream, try substituting a little crème fraîche. Use it to finish pan sauces and gravies, if you like. It’s rich, but a little goes a long way.
As for sweets, crème fraîche is my preferred topping for many fruit tarts, cakes, cobblers and crisps. It can be sweetened and whipped like regular cream if you like, or left plain. It’s fantastic in cake batters, too. Try it in truffle base or in caramel sauces that call for heavy cream. Do I even need to mention strawberries?
Crème fraîche will keep for at least a week in the refrigerator. Just don’t forget to start another batch before it’s all gone!
1 part buttermilk
8 parts heavy cream
(For example, 1/4 c of buttermilk for 2 c of heavy cream)
In a clean glass jar, combine the buttermilk and the cream. Cover loosely (it should be protected from dust, etc, but have a little room to breath) and put in a draft-free place. Give it a stir after several hours and, if it’s not thick, give it more time. It will take anywhere from 12 to 24 hours. The warmer your kitchen, the quicker the process. When it has thickened, put a tight lid on it and store it in the fridge where it will keep for at least 1 or 2 weeks.
To make the next batch, substitute some of the existing crème fraîche for the buttermilk.