the cherries over a bowl and reserve the juice. Set the cherries aside.
Stir together the flour, salt and egg in a small bowl until the mixture becomes a smooth paste. Stir in the sour cream
until combined, and then whisk
the mixture into the cherry
juice until all the lumps are gone.
Pour mixture into a medium saucepan
. Bring to a boil over medium-high heat and cook, stirring occasionally, until mixture thickens, about 8 minutes.
Remove the mixture from heat and stir in the cherries. Let the soup
cool completely and then refrigerate until chilled, about 1 hour. Serve cold.