1. Cook cucumbers and onions in melted butter, in a skillet, over medium-high heat. Add flour and blend with the pan juices.
2. Slowly stir in broth and cook until it begins to boil. Season with salt & pepper to taste.
3. Bring heat down to low and simmer, covered, for 10 minutes. Stir occasionally. Then refrigerate until cold.
4. Blend some of the mixture in a blender until smooth and then push through sieve into a bowl, throw away the seeds. Repeat until done with all the mixture.
5. Add half & half to mixture, stir well and serve.