Crème fraîche is soured cream, or cream that has been thickened and acidified by the growth of bacterial cultures. Often sold at specialty markets, crème fraîche can be used in a number of ways in the kitchen. For example, you can serve crème fraîche alongside fresh fruit, or you can stir crème fraîche into soups or sauces to add a little bit of dairy richness and thickness; it also contributes a bright bit of acidity to any dish.

Crème fraîche is incredibly simple to make at home: You simply combine cream with a small amount of buttermilk and allow it to rest in a covered container at room temperature for about 12 hours. The ratio of cream to buttermilk doesn't really matter all that much; add more buttermilk and you'll need less time for the cream to thicken (but it'll be less creamy). Add more, and it takes longer, but tastes better. We found one tablespoon of buttermilk per cup of cream (that's a 1:16 ratio) to strike the best balance.

This crème fraîche gets super rich and creamy at right about the 12-hour mark. You can also halt the process early by just refrigerating it to stop the bacterial action. This is useful if you want a thinner Mexican-style crema agria for drizzling over tacos or sopes. For those of you worried about cream spoiling at room temp, that's the idea: it's the good bacteria from the buttermilk multiplying in there that prevents the dangerous bacteria from taking over.