Crème Fraiche

1 pint heavy cream 2 tablespoons cultured buttermilk Pour the cream into large mixing bowl and add the buttermilk. Stir until well-mixed but do not whip the cream. Let the cream and buttermilk sit covered on the counter for 24 hours. After 24 hours, stir the cream and transfer to a storage container such as a Mason jar or Tupperware. Store in the refrigerator for up to 10 days.