Place the borage flowers in a small bowl, cover with boiling water and leave to steep overnight.
The next day, strain the liquid into a pan and bring to a boil. Pour this boiling liquid over another cupful of borage flowers. Soak for 8 to 10 hours. Strain again and press all the juices out with the back of a wooden spoon.
Measure the liquid and add 1 cup of sugar for every 1 1/4 cups of water. Heat slowly until the sugar has dissolved, then boil vigorously until thickened. Remove from heat, skim and store in clean bottles or jars. Keep in refrigerator.