Here is a simple recipe for making your own crema at home. Crema is similar to the French Creme Fraiche and has the flavor of a buttery rich and slightly tart sour cream
Place 1 cup whipping cream in a small saucepan on low and heat just until it is barely warmed. Do not overheat or you crema won't thicken. and 2 tablespoons buttermilk in a glass container. Cover and let stand at room temperature (about 70°F) from 8 to 24 hours, or until very thick. Stir well before covering and refrigerate up to 10 days.
The owner of this pot de creme cup describes it as being from the Napoleon III era from the Sevres factory in France