Heat the oil in saute pan and add the onion and garlic and saute for 7-8 minutes on medium-low heat (not browning) until the onion is transparent. Stir in the cucumbers and saute for about 3-4 minutes. Pour this mixture into a blender with the buttermilk (and/or yogurt) and the chicken broth. Blend until you have everything smooth.  Chill, stir in basil (or salad burnett) and salt and pepper to taste. You can adjust the consistency by adding a little more broth. Garnish with creme fraiche and serve in your favorite bowl or martini glass.