1 Whisk buttermilk with sour cream and yogurt until smooth. Season with salt and pepper. Rinse dill and finely chop. Rinse and thinly slice radishes. Finely chop about 2/3 of slices. Rinse, trim and cut scallions diagonally into very thin rings. Set aside some scallions for garnish. Stir remaining scallions, along with chopped radishes and dill, into buttermilk mixture. Season to taste.
2 Cut 2-4 slices of bread into small cubes. Cut 2 slices of the cheese into strips, and layer the rest of the cheese on remaining bread slices. Ladle chilled soup among 4 small bowls, garnish with remaining radishes and scallions, cheese strips and diced bread. Serve soup with the cheese-topped bread slices.