Crème fraîche. One of the best things you can keep stocked in your fridge. I've pulled together many a quick dinner with a spoonful of the stuff. It thickens without curdling, a little goes a long way in fast pan sauces, blend it with fresh herbs and a dash of fresh lemon and add it to a baked potato, chicken, fish...the options are endless. Or add a spoonful to fresh fruit for dessert.
One the very best things about crème fraîche is you can very easily make it at home.
Add 2 tablespoons of buttermilk and 1 cup of cream to a small glass jar. Use a good quality cream like Straus. Let the jar sit, uncovered, at room temperature for 12-36 hours (the timing will depend on how warm your kitchen may be and if it's summer or the dead of winter). Once it firms up quite a bit, stir and put in the fridge, preferably 24 hours before you'd like to use it as it will continue to thicken. It will keep in the fridge for about two weeks.