Set aside 8 to 10 blueberries for garnish, if desired. Place remaining blueberries in blender container. Set aside. In medium saucepan, beat together eggs, buttermilk, sugar, and juice until blended. Sprinkle with gelatin. Let stand 1 minute. Cook over low heat, stirring constantly, until mixture just coats a metal spoon with a thin film and reaches 160°F. Pour over berries in blender container. Cover. Blend at high speed until well blended, about 30 seconds. Pour into 5-cup mold. Chill until set, several hours or overnight. To serve, unmold on platter. Garnish with yogurt and reserved berries, if desired.